Oyster has been using MIFARE DESfire, and stopped using MIFARE Classic, for over a decade now.
They're stopping it for completely unrelated reasons (primarily convenience – people don't like having to buy and top up a card – and not having to maintain a vending machine and top-up infrastructure).
They're stopping it for completely unrelated reasons (primarily convenience – people don't like having to buy and top up a card – and not having to maintain a vending machine and top-up infrastructure).