If you are buying from a private seller with good feedback I would not worry about it too much. There is risk but if you pay with a postal money order they do take mail fraud seriously. I have sold guns on GunBroker and do not have a way to take credit cards and the same is true for most private sellers.

All the credit card companies require anyone accepting their cards as payment to not pass the fees they charge along to the customer. So the vendor has to eat the fee of up to 5% whenever someone pays with a credit card. Great for the CC companies and those of us with high fee cashback cards, bad for sellers and cash buyers paying the hidden VISA/MasterCard tax sellers have to add to the price everyone pays to cover the fees. Sometimes sellers can get away with offering a cash discount but some have decided to not accept plastic so they can offer lower prices. Not accepting credit cards does not always mean they are looking to rip people off.

But in general I am with you. Unless I know I am buying from a private seller I only do business with vendors that accept credit cards.