The intention is for the other end of the transaction to be faster.
Namely "cashing up" at the end of the night doesn't involve counting many items and taking them to a bank.
Unfortunately, it's very hard to verify a cashless system. If the publican believes that they took £1000 but the cashless provider claims they only took £900, how do you prove it?
With cash you do a recount of both ends - till roll and contents. Can't do that in a cashless system.
So the business must have 100% trust and confidence in the cashless provider. If they don't, they cannot afford to use them at all.
Equally, so must the customers.