Mainly due to credit card fraud - people claiming misuse of their CC after already getting their BTC, there is nothing the seller can do.
That's true. I have a feeling it would only be a small amount of people that would do that though. It's like people who buy something on eBay and claim it never arrived so they get refunded through Paypal and screw the seller. But then those people get banned from the service. I wonder if there's a cutoff time for being able to claim misuse of your card after a transaction shows up.
It is only a small number of people who would do this but they have spoilt it for the rest of us sadly.