It says lot about the show if he thinks it should of ended, the same who uses the same concept of stupid man and talking animal best friend over and over
Personally i think they show should have ended but thats just personal opinion, south park often has intelligent humour which is why i prefer it (but still is imature) where family guy is a show that just shows a series of gags and little story line.
The Simpsons also is not funny, you may as well ask why are the two on the air.
While Family Guy perhaps should've been cancelled last season or the one before, The Simpsons should have been cancelled season 13, it's now season 26 and it hasn't been funny since then. The Simpsons Movie was also a right disaster.
"Its not well written or funny" is a matter of opinion. Those who disagree with you, tune it... and it turn the show makes money. Even now after all these seasons they are still generating a profit. Thats all it takes.
Because people still watch it and it makes money... I don't like the show really, I don't watch it. But a lot of people do which is why it's still on the air. I mean a month ago, the show got 6,267,000 views.
It's catered to stupid people who can only comprehend toilet humor. That's like 80% of the US.
It's not well written or funny. The Simpsons is funnier and better written. I am not a fan of South Park, but at least with that series, it does have some funny episodes and moments.