There are still some things to solve for the cashless society.
1. Electronic transactions are still far too expensive. Every shop I go into to get (say) my lunch have a minimum amount you have to spend before you can use your debit card (or you have to pay a surcharge). My lunch always falls below this value so I must use cash. Things like vending machines too. Until it's cheap enough to use something like a debit card to buy an item costing 60p, then you'll still need cash.
2. Security. Debit/credit cards are too insecure, and the burden of making them secure is on the merchant in the form of PCI-DSS. It means if you're a small business taking debit/credit might not be an option. The burger van in the car park for instance, it's still impractical for him to take electronic transactions due to the equipment requirements and PCI-DSS.
3. Very hard to settle private debts. For instance if I hire a builder for a small job, he now has to give me all his bank details if I'm to do an electronic transfer. It's about 100 times easier to give him cash.