Because everybody and their genital warts thinks the show is just sooooo f*cking funny.
And it's not.
HAHAHA!! Far be it for me to speak for my genital warts, but they really have no sense of humour anyway.
Fair enough though. I feel the same way about the Simpsons. It actually drives me crazy to hear people talk about how funny "the new episode was". There's absolutely NOTHING new about it. That show ceased to be funny in '93.
The movie was OK (far from great), but that's only because I haven't watched the Simpsons in such a long time.
I find the Family Guy funny. Yes it's just a bunch of cut scenes with a story thrown in, but it's still funny. Sometimes it misses, or they take a joke too far, but that's half the fun of watching it. It's definitely not everyone's cup of tea that's for sure.
Anyway, Futurama was, is and always will be superior to both The Simpsons and the Family Guy.