Because on Ebay anything less than 5 stars is a negative against the seller.
Find about 40% of people never leave any feedback at all, of the remaining ones that do, unsuprisingly the ones who want to moan are the most vocal.
As little as three 1 star ratings, no matter positive , and happy customers who didn`t bother leaving feedback, will move your listings to the bottom of search and decimate sales.
Feedback ceased to have any real meaning to buyers on ebay sometime ago, only actually look it up on Toolhaus.org if its below 98% with a low total.
Amazon dosent play with search levels etc for listings, it allows plenty of space for honest feedback but can again suffer from happy customers who got the goods they expected in a timely manner don`t see it as 5 star service worth leaving feedback about.
Fact that ebays search dosen`t work properly at best of times probably accounts for Amazons share price being a multiple of ebays.
Ebay bought TV adverts, Amazon had loads of free plugs masquerading as `news` items from their distribution centres,
Ebay forgets who actually pays them, sellers.
Cheers Adam