I'm an achievement whore/hunter/whatever. I get achievements. I want my gamescore to rise. If you were like me, you would be the same.
It's necessary.
No game in my list has -500g. Well, except those games that suck, or those who have hard achievements.
If a game has achievements that would take too much time to get, or are too hard (L4D for example), I won't get it.