contactless payments work well if they can speed up transactions to reduce the length of queues. I recently travelled on the M6 toll and you can now wave your card. This works well because it's slightly quicker than posting your card into the slot. If, however, you were to use your phone for this it would be far slower.
1. unlock your phone
2. load the NFC app
3. choose the correct wallet
4 enter a pin to unlock the wallet
These are not steps you need to be doing when you're in a queue.
Paying in shops doesn't work either currently because to pay with your card you have to tell the shop assistant that is what you want to do and wait whilst they tell the till you are paying by card and only then can you wave your card. The system needs to be
1. shop keeper says that'll be £3.49 please
2. customer waves card
Until the system works like that it's a waste of time.