Yeah, I never really like that thing, either. The low ratings are actually worse than negative or non-constructive reviews, in my opinion. And if you see a one-star story getting great reviews, even constructive ones, you're gonna think, hm, something's not right here... Oh, and I'm sure we've all seen a five-star story with awesome reviews--eleventy billion of them but the story itself is absolute crap.
Myself, I tend to get a little worried when people aren't reviewing my stories. It could mean that people are only looking at it because it somehow ended up on Godawful Fanfics or being MSTed or some shit. Or people just clicked on it because they liked the title and summary, but since I like uncommon pairings, they'll turn away, regardless of the content.
But, I don't want to criticise too much on reviewers, since they could be shy, like me. Or maybe they feel too much pressure from the authors who bellow in their ANs that they only want constructive, page-long reviews, and well, we're busy people. This is only a hobby. I know we've got a lot of seasoned people here, but no one's getting paid for doing this stuff.
So, yeah, this is a good way to console myself. I'm not getting paid (else I'd get the pants sued off me), so there's really no pressure. And if my story's in progress, I can understand that people will want to wait until it's finished so they can actually write their thought-out review, and maybe even recommend my story.
Yeah, sorry this was so convoluted.