I'm not sure who is even saying that.
I've owned a ton of amps (still, not even close to some people on here) and yeah some of them, you kinda have to shake your head and think that maybe the designers were really fucking high when they decided where their EQ setting would sit. The Krank Rev 1 comes to mind.
But having said that (and here I go repeating/re-stating) the majority of the amps I've owned really did sound very decent (in a band setting, because that's how I use my 100 watt heads) with minimal deviation from the middle (noon) settings. Does that mean I set the knobs there and never touched them? Fuck no. Who the fuck would do that? That's the dumbest shit I've ever heard. Also, I feel it necessary to point out that I don't really give a flying fuck about clean tone.
I'd be interested to see a poll of how many dudes here actually play in a band versus how many are just into recording or bedroom playing. I'm certainly not knocking those who don't play in bands. God knows, it's sometimes a massive pain in the dick. But I do think it is a HUGE factor in how you use your gear.