Yeah, and it would be hard to ban people for abusing the stars when you can't know for sure the motive behind their rating. If readers were going to get banned just for rating a story one star out of five, there'd be no point for having the star ratings at all. They could give a story one star because they're jealous or don't like the author, or they could give a story one star because they legitimately think it sucks (and maybe it legitimately does).
There are stories on AC that, if asked to honestly rate them, I'd give one star. But I don't review stories that are that bad; as Thumper's mom would say, "If you can't say something nice, don't say nothin' at all." I remember the stars being there, but I don't remember really even using them; I didn't review much back then because I didn't actually read much on AC back then. All the stories I followed were on other sites.
I do remember the drama, though, when people were getting flamed and unfairly rated down for no legitimate reason, and we don't need that crap happening again. We're better off without them.