It's a reflection of the society it's made in as much as anything else. Christian based cultures have always had a very stiff attitude to sex, which, when combined with this 'new medium' seems to send people into some kind of mild frenzy. Compare to Japan, which has been putting sex in computer games for years (though they never make it west, obviously).
Look at Mass Effect, it has a sex scene less explicit than that in titanic (PG-13) and suddenly this is a 'big thing' that everyone is talking about, rather than just 'the norm', as it's become in film.
Another example would be Hot Chocolate. It was a joke more than anything else, and yet look at the reaction.
And all this is the reaction from people who simply didn't grow up playing computer games, but who DID grow up watching films.
My prediciton is that, give it another generation or two, when the people who grew up on computer games are in the posisions of power, and everything should stabilise a bit.