Why are Rated R movies so Stupid?

I don't know what you mean at all. The R rated movies I enjoy are usually dramas, independents or some other genre.

What you described is the "Idiot Frat Boy" movie genre. Also the "Idiot prepubescent teen movie" genre. Both are formula, carbon copies of the same type of movies since Porky's.

Not all R Rated movies are stupid. It's the movie itself that makes it stupid. They're have been tons of stupid PG movies and G movies.

One "R"-rated movie which I've enjoyed greatly lately is Charlie Wilson's War." It has a wonderful cast playing engaging characters in a story which would be near unbelievable ... were it not TRUE! I personally think it's a massive hoot and I recommend it to ANYONE ... over the age of 17, of course! [chuckle!]

It has become more difficult to get an R rating for a film these days. Many good dramas sometime fall into this catagory. The comedies want to seperate themselves from the kid friendly family fare so they will throw in whatever it takes to get the R rating. Some producers will intentionally throw tons of stuff in to see what the censors will and will not allow. Borat was a good example of this kind of censorship warfare. He put in so much disgusting over the top stuff they only took some of it out. Even Sasha Cohen was surprised with what they let him get away with.