Yup, hobby.
I'm brought to it via a love of music like many here. But I have a fascination with the gear aspect and have certainly spent enough time on that side of things to warrant calling it a "hobby." (Though I admit to being a bit equivocal about that term. I'd feel more comfortable using it if I actually was involvedin DIY stuff rather than purchasing. But then, I'm quite involved in the putting together, setting up and optimizing of my system, including room acoustics etc).
One of the more annoying tropes in the audiophile world is the "It's all about the MUSIC" "I'm only in it for the music." It's a sort of purity test or social signalling in the audiophile world. It's seen as the purest devotion and "those other audiophiles who listen to their gear and care about all that stuff" aren't about the "real goal." "Audiophiles who are really into the gear have lost their way." And yet it's typically audiophiles who spend crazy money on gear who say this. I was at an audiophile's house who had probably around $200,000 worth of gear, multiple amps, hose thick cables held up on cable risers, the whole shebang. When he told me "I'm only in this for the music" I was thinking "Yeah, right, who are you fooling thinking that other than possibly yourself?"
But that is NOT to denigrate anyone's interest in the gear/technology side of audio. As I said, I happily admit an ongoing fascination with it, and clearly many here are also gear-geeks, enjoy building, measuring things etc. If an audiophile has a $200,000 system and only 10 CDs he ever listens to I'm not going to judge that as if I'm in some more rarified position to do so. Whatever floats your boat.
It's only irritating insofar as audiophiles won't own up to their actual motivations, especially in terms of portraying (or imagining) their motivation as more dignified than the other guy.