The general running gags in cartoons

It's not like I don't have anything better to do with my life, but I'd like to talk with you about cartoons. Again.

Cartoons are there to entertain us and nothing else. While they are supposed to be dumb and unrealistic, some of the general running gags are really overused, while they aren't even funny or slightly make sense.

I discussed the "bagpipe hate" in cartoons before, but how many of you still remember those scenes from..well, any cartoon, where a character tries to open a door while basicly pushing the door back with her/his feet? What is up with that and what's the logic behind that?
Another overused joke is a character burping in the most gruesome way possible after (s)he just devoured something. Nobody likes the sound of burps, yet it appears in so many cartoons, it makes me wonder who even thought it was a good idea to begin with.

There are many jokes like these that pretty much all cartoons use. Are they doing it unconsciously, are these jokes just good episode fillers, or am I missing a sense of humor?