Majority of payments on ebay and amazon are done with reversible methods, that is just how normal business operates. Most customers are honest people that aren't looking to scam but this forum has a larger amount of nigerian scammers than usual.
If you want to be in business for real, you have to accept reversible methods like credit cards if you want to actually attract a large amount of customers.
A lot of online payments in my country go through payment processors via a payment gateway where the buyer logs into his bank account giving an authorization to a specific transfer, or debit cards are used where it's harder to commit chargeback fraud. I think it's mostly Americans who use credit cards day to day, in Europe they aren't as common.
It's also easier for a larger online store to swallow a loss from chargeback fraud, as opposed to a random person who sells a Casascius coin on eBay later to find out the buyer makes up a story and essentially gets a coin worth thousands for free.