It seems they have this policy as it is cheaper to deal with an unhappy seller who has little/no protection legal or otherwise (especially if they have used thier PayPal balance for payment) and who will generally not chase them through the court system (in which case PayPal will argue it is a case between the buyer and seller, not PayPal and the seller), than an unhappy buyer who often has the backing of thier credit card company (or bank) to fight chargebacks on thier behalf and in most cases win.
As a vendor/retailer, especially if you have your own ecommerce store or sell high value items, be VERY wary of PayPal and only ever complete transactions if all buyer details match and protections are in place (buyers are verified and items sent only to card billing address).
Posted something similar a while back, http://news.ycombinator.com/item?id=361361, and it is sad to see little has changed.