Why does Family Guy play constantly on television but Simpsons and South Park are only shown at certain times?

Because they can make more money selling commercial time for Family Guy, since the key demographic also happens to be the age group that advertisers go for.

Family Guy is more popular so gets more views. The other two series are older and more familiar to people.

Family Guy is still being made at a remarkable pace whereas the other two have larger time between series’. I have no proof but it certainly seems that way.

Because family guy has alot of sex scenes. People. Enjoy. IT!!

Family Guy is better than the other two by a long shot.

I’m thinking it depends where you are. The Canadian network Global plays The Simpsons all the frakkin’ time, and it also plays on other Canadian stations a lot.