Why are there so many valve amplifiers on the market then ?
Mostly for the same reason as there are £100+ t-shirts out there - pure vanity and people believing in market hype.
There was a good reason guitarists liked them at one time but that was because of the type of distortion not purity, exactly the same sound can be reproduced much more cheaply now.
Mind you, I still have a very early hybrid stereo tuner which I can't seem to let go.