People buying things can file a claim to say that they paid for the item, yet did not receive it. Paypal tends to believe buyers more often (in my experiences i have been able to easily get money back from fraudulent sellers without necessarily proving anything. It was just my word vs his). IF the seller didnt have proof that what he sold had been delivered, it could be conceivable that someone could scam someone by buying something and get their money back while still getting the item.
For big purchases, I would rather deal with banks and people that i KNOW i can trust. Anytime I've bought a motorcycle from an individual at a distance, I've talked to the people at his bank and sent them a check. When i bought my 675 i just wired the money to RD, but i still communicated with people at the banks. I didnt have a problem wiring it since i feel like i can trust such a big company with a good rep. For individuals, I have less trust.