I got fooled on eBay before, but it doesn't happen just with PayPal.
I worked in retail for the last couple years and understand why companies do that.
All they care about is customer service, overly satisfied customers so they will do anything to keep customers happy, and they will come back and shop more/ use their services more.
For example, in stores customers would buy lots of items when they are on sale (let's say 40%), then they will return it without the receipt at original price and get a gift card for the amount they spent + 40% extra. Then sell it on eBay, = profit..
It's like getting free credits to shop, less hurtful bit still...