Hollywood and its fixation with toilet and anatomy humour

I have never found America's fart/shit/pee jokes funny. Not that I find it disgusting, (they are perfectly normal human functions), but I don't see the logic. How can you laugh when someone has just dropped a load and has no paper to wipe his a** clean? What is so funny about that? I just don't get it.
Despite my reservations about Hollywood's obsession with toilet humour, strangely, I have shared a laugh over certain other jokes, that would otherwise be deemed crass. For eg: In, There's Something About Mary, I cannot help but laugh at Cameron Diaz wiping off presumed hair gel and fixing her hair. That was hilarious I thought.
That apart, coming back to my point. I recently had the fortune (or was it misfortune) to watch Jude Apatow's 'Knocked Up'. Gorgeous, smart, but piss-drunk gal picks up ugly, jobless and unemployably uncouth (uh! I wouldn't want to be seen with you kind) guy gets knocked up in a one night stand. Less said the better about this movie that is all about tits, getting laid, balls and more of it. In a nation like the US, that I consider relatively progressive about under-the-blanket activities, I find it strange that jokes about desperate men trying to get a glimpse of a woman's anatomy are Hollywood material.
What makes it worse is that I have now started watching Jude's latest movie 'Superbad' about teenage kids and their almost sexcapades, with lots of innuendos and tit/balls/sex jokes thrown in.
Frankly, I am to blame for attempting to watch something i dont like. I am not uncomfortable about discussing sex, but the Hollywood version is downright cheap.
But then, this is what the world wants to see... a forty year old virgin getting laid, or a gal getting knocked up or maybe just a 15 year old getting there... it is all entertainment and believe me, with people showing studios the money, there's gonna be more of tis shit!