Why don't cash points use fingerprint readers instead of PIN number?

fingerprint readers are notoriously unreliable, and require a manually inputted password as a backup for when it does not work. Your cash machine is basically a very low spec, limited hardware, network device. It connects to the banks network, accesses the data and verifies the card data against the stored data, to verify a fingerprint takes time and resources, both of which the machine has very little of. To disable a machine all you need to do is scratch the scanning glass, expensive and time consuming to replace and they need to be accurate. A simple marker pen will be enough to render the machine useless, the criminal element would simply fit a cover on the machines and con hundreds in a few hours with a false fronted ATM machine. Perhaps slightly more worrying is that of course you don't actually need to be attached to your finger for someone to withdraw your money.