There is no reason it would need to increase friction per transaction. Right now to make the first purchase at a merchant you have to type your bank account or

There is no reason it would need to increase friction per transaction. Right now to make the first purchase at a merchant you have to type your bank account or credit card number into the merchant's website. Instead the merchant would redirect you to your bank's website and you would authenticate with your bank. How is that any more difficult? It's just more secure, because the merchant is no longer in possession of everything someone would need to make fraudulent charges to your account at any other merchant.