Have a seat, this might shock you.
Really, sit down...ready?
They're there to make you feel like you achieved something.
*falls over in shock with you*
The PS3 has these as well, although only for newer games. The just give you goals..some of the achievements, maybe 2 per game, are for bragging rights. Next-to-impossible to get achievements. Not all games have them either, but games that have them are smarter for it, especially if it's a decent game. Makes people not just want to beat it, but play it until they can tell their friends they did the unimagineable.
I don't care for them a whole lot..I like to unlock them, but the majority of the achievements/trophies aren't supported over online play, which is the primary venue through which I play video games, so I enjoy unlocking what I do, but never try to unlock them all.
