Technically correct speakers make good references for evaluating recordings but they are not necessarily the most musically enjoyable speakers to everyone. Yes, average listeners in laboratory settings prefer a flat and smooth frequency response, but many audiophiles see the sound produced by their system as something which they have built to explore music according to their taste and understanding. Musical taste has a lot to do with it - how can one 'correct' speaker be ideal for everything if recordings vary so much? In this sense, a technically perfect speaker becomes a jack of all trades and a master of few. If you listen to ancient jazz and blues recordings, or solely to classical, or modern electronic music, the ideal speaker will vary. A speaker with low distortion, flat FR and smooth directivity transitions will probably not sound terrible on many recordings, but we can't really blame people for liking the sound of dipoles, or harbeths, or horns, altec coaxials, line arrays, and any other number of fundamentally compromised but beloved speakers.
It is not simply an issue of marketing or the incompetence of the designers. Audiophiles simply have different goals than neutrality, and speaker designers provide them with options.
You bring up some good points. Though to your point about different speakers being better for different genres, I can see this being true to a certain extent, but I feel there's enough variation within the confines of "flattish" response and "smooth" dispersion to accommodate for genre differences and individual preferences. The NRC and Harman studies seem to suggest these qualities are largely beneficial irrespective of genre (along with bass extension, not to be ignored).
Certain genres seem to 'dampen' the difference between speakers, but I've not seen anything to suggest a specific type of music will cause people to
prefer a speaker with a particular idiosyncratic sound over the flattish one. If anyone has research suggesting otherwise, I'd love to read it! I've seen individual manufacturers claim their speakers perform better in blind tests... but not seen the data to back it up.
Of course, there will be outlier individuals, but that doesn't seem to be a good demographic for a speaker company to base its income on...
Moreover, I rarely see speaker companies themselves claim their speakers are better for specific genres or designed with a particular type of music in mind. Maybe there's a speaker that's perfect for jazz-infused k-pop with a smokey vocalist, but marketing materials are more likely to say something like "hear music as the artist truly intended!", (something studio monitors and neutral speakers seem closer to replicating than esoteric designs.)
Again, don't get me wrong. I'm fine with listener preferences. Speakers shouldn't sound exactly the same. Buy what you like! Heck, make your choice purely on aesthetics if that's paramount to you - aesthetics factor strongly into my own choices. But to me, the value of the Toole/Harman research is... well, value.
Much in the same way Amir has shown you don't have to spend a fortune to get an audibly transparent DAC, the Harman research shows the point of diminishing returns among speakers can begin a lot cheaper than people assume.
You'll often hear audiophiles say they make their choices purely on sound quality, but blind tests appear to reveal this is often not the case.
Measurements that correlate with listening preferences keep us honest.They ask people to reconsider why they're spending multiple grand on a pair. And they suggest that if a speaker company is charging out the wazoo primarily on promises of sound quality (rather than design, build quality, or features), it better have some state of the art performance to match.
Of course, there still are always "phantom images" between adjacent speakers in stereo and multichannel.
