Why is everyone so obsessed with ratings (on this sub)?

I see at least one post a day asking about how to avoid a negative rating on Amazon or eBay, and I just don't get it. When was the last time you looked at a rating to make a buying decision? I've purchased from eBay buyers with ratings in the high 80's, and I honestly cant say I ever look on Amazon.

Whats the deal here? Are people just fascinated with the 100% I cant imagine there is a huge difference in sales volume (unless you are in the mid 80's)... Thoughts?