I remember going to the drug store during the 50's they had a tube testing machine and he would test the tubes and get new tubes at the store to repair the TV when the old tube went out.
Most of the tubes used in audio equipment today were designed to be used with tv's and not for audio use.
I don't know about most but what I see I think was used more for radio, radar and PA first.
All I know is that all audiophiles should be banned from the use of any tubes commonly used in vintage Fender, Vox and Marshall guitar amplifiers, and all of the modern variations on those classic designs. The remaining population of NOS tubes of those types should be used for making music. Just sayin'....
In high-end audio, you can't even fight an opinion with the facts.