Dcstep,
Manufacturers pick the tubes they put into new equipment based primarily on practical considerations -- cost, reliability of continued supply (meaning new, not vintage stock), and reasonably good sound.
But, there is no way for a manufacturer to know what sound any particular customer would favor based on that customer's taste and complement of other equipment. Given differences in taste/need, it does not make sense for a manufacturer to spend a LOT of money on NOS tubes that may actually sound worse to a particular customer.
There is no consensus on what is "better," that is why the ability to make changes to the sound by the relatively simple act of changing tubes is a good thing.
Manufacturers pick the tubes they put into new equipment based primarily on practical considerations -- cost, reliability of continued supply (meaning new, not vintage stock), and reasonably good sound.
But, there is no way for a manufacturer to know what sound any particular customer would favor based on that customer's taste and complement of other equipment. Given differences in taste/need, it does not make sense for a manufacturer to spend a LOT of money on NOS tubes that may actually sound worse to a particular customer.
There is no consensus on what is "better," that is why the ability to make changes to the sound by the relatively simple act of changing tubes is a good thing.