at the very least it gives you confirmation of whether you like it or not; you'll never know unless you listen to it (at least once). two people with very similar taste overall can have albums here and there which are quite different which the one likes and the other doesn't: no two people's taste is the same. it's a understandable heuristic, to a point, to primarily seek top-rated albums in a genre you already know you like (to a greater or lesser extent), but it's not a foolproof method for finding music you'll enjoy. if you look far enough, there are going to be cases where a group of people rate an album poorly or average which you happen to like.

Why would anyone look at any ratings is beyond me.