Well, it really doesn’t suit itself for automation, much less for real-time transactions. Say, you want to sell access to an article on your website. It would be cumbersome for the customer to have to switch over to their online banking and typing in all details (ok, today we have QR codes, but you still need to jump through many hoops, much more than with, say, a credit card or PayPal payment). Then it takes time until the money shows up in your account - sometimes several days. And, finally, there was no API access available from the banks for small sellers that would have allowed them to build an integration, even if they had the resources to write custom software.