A very big Walled Garden. As an owner of an ecommerce site, I can tell you it's very tempting to create an App version just to take advantage of one-tap thumbprint orders.
Also I don't think Amazon or Google have a TouchID payment system.
Also I don't think Amazon or Google have a TouchID payment system.
The point was it used to be easy to use their services outside in the open internet on normal websites like Paypal.