Who said “ flat freq response “ is the best?

I have a dumb question?

who determined that the “ flattest frequency response” is the BEST?

we are all looking over specs and note all the +\- dB deviations from flat and declare it bad?

are we cattle? Or did someone like J Gordon Holt declare it?

 Or am I missing something 

Anyway, I think about stuff to much...lol

jeff