>>105642665 (OP)Because it's a lousy business that's only worth to the OS makers themselves.
You only get a fraction of a percentage of the payment value - most remains with the issuing bank and another much smaller chunk to Visa/Mastercard. The only way to make decent money out of it is by having exceptional scale, which only the OS makers can hold. No app maker for digital wallets could ever get enough downloads to make it worthwhile. There is no possible product differentiation.
Only the issue banks themselves could get enough traction with their own cardholders, but they already get the lion's share of the money spent on credit card payments, so they literally don't bother.