Vacuum tubes versus solid state in specialist audio
"...large body of opinion..." Well, in my opinion, some "tube people" shout louder than others. Most people listen to music from their phones, that's all solid state. If we count these in, the "tube people" are a minority. Indeed tube or no tubes is a matter of opinion and personal preference.

I think that there is a contradiction regarding audio equipment using tubes. On a testbench I can prove that tubes can add distortion (depending on how they're used), some people prefer this which is their good right. Listening to music is for enjoyment. If using tube based equipment gives someone more enjoyment then by all means, use tube based equipment.

Also in the audio scene "fidelity" and "neutral audio equipment" (which does not affect the audio signal) is regarded highly. Since tube amplifiers "do something" to the signal that contadicts with this. So if you would take this "something" and put it in a DSP then you deliberatly admit that you're changing the audio signal. Some "audio people" think this is "not done". Using tube based equipment is much more accepted and sometimes a sign of sophistication perhaps ?

So although I agree with you that the same or a very similar effect could probably be achieved using a DSP I don't think there's much commercial value to be earned.

And I guess many people just like the soft glow of a tube :-)