"Because the extreme high end wants a certain sound and imaging that has changed over the last several decades.
The current trend is:
Exaggerated high frequencies and etched sound = "detail", biting unnatural attacks = "fast transient response", and unnaturally dry bass = "taut" and “tight" "
Good argument. Fashion shouldn't be an issue when it comes to audio playback.
Yet it often is, as any visit to a high end show will usually demonstrate.
One explanation given by a certain UK reviewer is that this is done as an attempt to grab the listener's attention as fast as possible. Particularly the elevated treble issue so commonly seen in many speaker designs which can give the impression of superior detail resolution in the short term - but lead to fatigue and headaches in the long.
Some used to even talk about sonic tastes varying from country to country, eg a French sound, an Italian sound, a German sound, or in America, an East and West coast sound.
I wonder if this is still the case?
Anyway, as far as tube amps go, weren't Single Ended Triode (SET) amps the most representative of the classic tube sound of yore?
https://hometheaterreview.com/whats-so-irresistible-about-a-single-ended-triode-set-amp/