Because of extra services. Unlike emails, which usually come with no guarantees or support, the money-sending services are protected. Even with something like EFT, consumers have 60 days in case of actual fraud or bank mistakes, and with credit cards, you are also protected from things like product non-delivery.

Those protections exist and cost money - both to pay for customer support handing those, as well as to reimburse customer when the original money cannot be found anymore.

(And related, this is one of the big problems with cryptocurrencies: most people are not happy to know that one typo / software bug means their money is lost forever. Those protections on regular baking are there for a reason.)