In an ideal world, each and every submission would be of equal quality and/or standard....but it ain't an ideal world, so there needs to be a way to control/limit band-width demands. This is the raison d'etre for wallpaper moderations and skin 'rating'.
Now, by limiting those who have access to the 'rating' function to 'peers', or those who actually [hopefully] understand the ins and outs of skinning, you 'should' get a more 'informed' rating and/or comment, circumventing the 'wow, this ownz', and 'you sux0rz' type of dross that really helps no-one.
Now, egos being what they are, no 'ratings' will ever be universally accepted......pride gets hurt, toes are stood-upon....but take it in the spirit it is given - to simply maintain some semblance of control of what might ultimately have become an unmanageable monster.
More often than not, I've found that anything with a particularly high 'score' shows an equally high standard of polish/execution, and vise-versa....the same being said for those of 'lower' score and their 'quality'.
[note to self....ease off with the 'quotation marks']..
Anyway, as Paxx maintains, if you don't think much of the 'ratings', just ignore them...