You pay for the product, they hand it to you, you leave the store.

You want something shipped, unless you have established credit, you pay, they ship.

Yes, it's postal fraud if someone collects a money order or check that you mailed, and doesn't ship. So you do have some Federal protection.

Paypal is the easiest way, and although some people want to mail checks or money orders, I don't care how they send it, as long as I get paid. Then I ship.

Now and then I just transfer the money into my bank account and in a couple of days, I'm paid. Meanwhile if I want to bid on "stuff" I have a nice and fast way to pay.

It's easy all around to use Paypal. No fees for buying a money order, no checking account fees, no postage, payment is confirmed to the seller in seconds. The buyer also has a confirmation that they paid, in case there is any debate over lost mail or other problems.

For most business involving goods, you pay first, receive second. For most services, you get the work done first and pay later.

If someone is suspicious of people who want to get paid first, how much more suspicious is it for someone to say, "ship it first", I'll mail you the payment later? It's reversing the standards of trade.