[quote name='Badge Man']Well what do you people want achievements or...?[/quote]
It's a token of completion, like a merit badge in Boyscouts or a challenge coin.
It's a signifier of accomplishment within the community.
If you aren't involved in the Live community then achievement points are not something you are likely to
"get." Some people like to check your friend's game list and see what he/she is playing and how far they have come.
Some become elusive and others are hard earned, take for example the Elite level in RB6:Vegas; chasing that was fun and it made the rank system more relevant.
I personally didn't get interested until the "Old Spice Challenge" contest where my gamer points scored me some nice free schwag (fake MS-money and an arcade DL of Contra . . etc).