I am much more likely to buy something if I can pay with a credit card. Making a wire transfer is stressful; I'm worried that I got the wire instructions wrong, and my money will go to the wrong place and be gone forever. Paying with a cashier's check is stressful; I worry that I will get mugged between the bank and wherever I'm spending it, or that I'll just lose it on the way. Cash isn't quite as bad, and I almost always have some cash on me.

But given the choice of paying with cash or credit card, I will almost always choose the credit card. I like the idea that if I walk away from that transaction and then later realize that the merchant sold me something defective or outright fraudulent, I will have some recourse in getting that money back.

I get that a merchant will prefer an irreversible transaction, all else being equal. But I don't think all else is equal; I absolutely buy the GP's argument that purchasers will be more liberal with their spending if they don't have to worry so much about the merchant being a scammer. And regardless, there are many many more purchasers than merchants, and most (if not all) purchasers would at least have a slight preference toward a reversible transaction.