It's cheaper. More importantly, it's more secure, because it uses my bank's security system and doesn't rely on sending "secret" information like credit card numbers to unknown parties.

Everything is handled by my own bank, and if I don't trust my own bank, I can choose a better bank and use that. With credit cards, I have to use whatever payment provider the merchant uses, and either they or the merchant can hang on to my credit card number, which weirdly is sufficient to access my money. Also, there are only two credit card providers that really count; not a lot of choice there.

Chargebacks may seem attractive as a buyer, but they also mean that a seller can lose their money after they legitimately sent the goods. Merchants would have to track down individual customers to sue them to get their money back.