I just want to address this a bit, as this confusion about why someone would choose a piece of colored piece of gear when more neutral options are available, comes up often enough. Some people know that, yeah, people have preferences, but they just can't wrap their head around WHY anyone would have an alternative preference.
If classic amplifiers had different sounds, it has to be true that all of them (except possibly for one of them) altered the sound. You and I have very different notions of what an amplifier is for. I would not find it useful to have an amplifier that could replicate the distortion that various older amplifiers introduced. To me, the idea that this is something that would be thought desirable is just weird. Why would I want to hear the distortion that a bunch of old amplifiers introduced to the sound? I just don't get it. I want the sound that comes out of an amplifier to be exactly the same as the sound that went into the amplifier (in the form of an electronic signal), and as concerns old amplifiers where the sound that came out wasn't an especially good match to the sound that went in, I have no desire to hear this except maybe once to satisfy morbid curiosity. Certainly not on any ongoing basis. Clearly, you and I have fundamentally different concepts for what an amplifier is for.
Note that the desire to avoid coloration in amplifiers is essentially the same for any piece of gear. For instance: Why would one every choose vinyl as a source when there are more neutral, accurate digital sources available?
Answer: Because vinyl tends to sound different, often due to coloration, and some people enjoy that particular sound. Also, there are aesthetic aspects of music collecting/listening that attend to vinyl, which some find enhance the experience.
Question: Well, if you like coloration why put it at the source? Why not introduce it later...via..EQ and/or some plug in you can maybe implement that mimics vinyl distortion?
Answer: Why? I get all that just playing a record. I don't have to bother fiddling with EQ or chasing down and implementing plug-ins or whatever. I just buy a record and play it and it does what I want. Plus, I like the other cool aspects of playing records.
Essentially the same answers can be given for why someone might buy a tube amp (like me).
But how do people arrive at these seemingly divergent paths?
Let's go back to our first encounters with "high end" sound systems.
In my case it was when my Dad brought home Kef 105.4 speakers and Carver amplification. I vividly remember the shock of hearing "imaging and soundstaging," 3D depth and timbral realism. I remember listening to Phil Collins singing The Roof Is Leaking and thinking just how *real* it sounds, like I'm peering in to the acoustic listening to Phil singing right there!
Many years later, long after leaving home and leaving that system behind, I had another eye-opener. My friend who got bit by the audio bug bought Quad ESL 63s and invited me over. Most people can remember their first listen to Quads or stats or panel speakers. That presentation I'd never heard before where the colorations that usually attend box speakers, that you don't even think about until they are gone, didn't seem to be there. A clarinet being played through the speakers just sounded like a clarinet hovering in air playing, clear as day. Everything took that step towards More Real sounding.
When I play my 2 channel system for guests, that is overwhelmingly the impression they express. It doesn't matter if the source is a good digital recording, or a well recorded record. The talk about how much more "real" things sound, more than they thought possible because they never really thought speakers "could sound real." The last guest said "That was amazing. It felt like I was sitting in the studio listening to the musician playing live!." Like me hearing the KEF or Quads the first times, they had no idea how the tracks were recorded, what equipment was used, the original room acoustics, whatever manipulation was used. They had no idea what if any colorations were being introduced in my equipment. All they really knew and reacted to was The Sound - how music sounded through the system - it had aspects that mimicked reality.
So it shouldn't be surprising that at least some (if not many) people impressed by sound this way carry on pursuing "how the system sounds" or "a sense of hearing the real thing" as their goal or benchmark. It doesn't mean at all that perfect recreation of reality is attainable. It's generally not. But getting
closer to
certain aspects of "real sounds" that someone cares about is a perfectly reasonable goal. It's an unattainable goal that you can only perhaps get closer to. But then, so is trying to hear the sound "as the original mixer/artist heard it" as well! (And I don't think that, in fact, pursuing the former necessarily departs that much from the latter!).
And of course others may not necessarily be smitten with how a sound system mimics real acoustic sounds. Maybe they are more in to electronic music and notice "listen to that slamming bass! Those crystalline highs!" And maybe they pursue simply "sonic attributes I like." And there can be a mix "I want it to sound more like the real thing, but there are also some sonic attributes I find that make me like the sound better."
So to bring this back to an example of tube amps, using my own preferences: The things that get me to plant my butt down and listen to music on a sound system are, first and foremost: certain sonic qualities of timbre that appeal to my ear and qualities that mimick certain aspects I percieve in real life acoustic sounds. I find most reproduced sound to be to electronic, to edge-oriented, to hardened, squeezed down and skeletal, and harmonically bland, relative to the real thing. I find that certain tube amp colorations seem to introduce a certain ear candy factor I like AND also introduce attributes I associate more with real voices and instruments: more richness and body, roundness, dimensionality, clarity without edge, a certain organic texture etc. Whenever I compare the tube amplification to the SS amps (as I've been doing again lately) things just sound that much more relaxed and natural to my ear, making me sink in to the "illusion of live" more effortlessly. And it makes listening more easeful. It's subtle differences in the Big Picture, but to me of great significance to my enjoyment. And I get this with seemingly very little penalty in regards to hearing the essential sonic characteristics of the recordings. There is NOTHING I can hear that goes missing in the variations in production quality, artistic choices, track to track, when I'm using the tube amps vs solid state. So to me it's a big subjective gain without any major penalty of "disguising the artistic intent/being grossly inaccurate to the recording." Because I ALSO want to hear the essential characteristics of recordings and production. With my tube amps I get just enough nudge in the direction of "organic" that I want, while maintaining the ability to hear recordings change in a chameleon-like way track to track. Again: my system is good enough that we can evaluate fine differences in mastering or recordings brought over by musicians.
So...why add this coloration at the amplification stage? Why not keep it neutral and add this coloration down the line?
Similar answers to the vinyl questions above: Because my tube amps do EXACTLY what I want. I just turn them on and they do it.
I don't have to go fiddling with EQ to try to mimic the tube sound (I actually tried early on and couldn't do it). Or go searching for ways to incorporated tube sound in some other part of the chain, additional gear, plugins or whatever. It's just set and forget and I feel no need to fiddle.
Also, like vinyl, tube amplification brings aesthetic pleasures I don't get from SS amps. I love the look of tube amps. Love the history tube amps represent. Love the glow of the tubes. Love the fact that in the glowing tubes I'm actually SEEING the music being amplified before my eyes.
Little things like this add to the experience IF you like them.
So there's a rational. It's not that we diverge that much, in the big picture. I do want a certain level of accuracy: I want to be able to hear quite acutely the differences between recordings. I don't want a coloration so overt that things start all sounding the same. I just want enough coloration that adds an additional pleasing quality and which nudges the sound in the direction of "more believable" to my ears, but which allows me to hear the distinct characteristics of recordings. And the amount of distortion introduced by my tube amps seem to do exactly that! They just nail this goal, leaving me feel little need to fiddle with EQs or other post-amp coloration devices, so why would I want to keep using them?