This is largely because of banking cartels boycotting Apple Pay.
The banks are trying to protect their incumbency status by not offering Apple Pay services to their customers.
That's not the issue in the U.S. Tons of banks are on board with Apple Pay -- including many, many small local and regional banks.
The problem with Apple Pay in the U.S. is that many merchants are not on board with it either because they don't want to update their POS equipment to equipment that supports NFC or, if they do upgrade their POS equipment, they purposely disable NFC on it because they want to be able to track the purchases their customers make (which I gather they can't do if the customer uses Apple Pay).