I can tell you exactly the problem from MY own personal point of view.
1: So many, even LARGE companies don't support contactless payments yet.
2: Those that do (and I've been asking) seem to have a £30 max limit.
3: So those two things combined mean you HAVE to realistically carry your wallet with your plastic cars/cash when you go shopping anyway.....
4: If you ARE already carrying your wallet then your current plastic card (which does contactless payments itself is jt a couple of seconds away, and even easier than getting the phone out your pocket.
So what's the point?
I wait say 30 seconds or a few mins to get served at the checkout, I've already got my thin, lightweight plastic card out ready in my hand (before I get to the checkout)
The current Chip & Pin process that works EVERYWHERE and for ANY AMOUNT is so quick, simple, really getting your phone out, hoping the shop supports it, and making sure you have not gone over the money limit supported, just really means by bother.
The current system is easy, quick, reliable, and trouble free.
Thats the problem right now. No one is desperate for this combined with the fact that right now it's worse than the system currently in place.