The thing I don't get about the UK is that they have very pervasive surveillance set up both online and in the real world, yet anyone can buy a mobile phone and

The thing I don't get about the UK is that they have very pervasive surveillance set up both online and in the real world, yet anyone can buy a mobile phone and a prepaid SIM at some random Tesco's and pay with cash without giving their name or ID. Why do they keep allowing this? Other countries have always required presenting ID to buy a SIM. It's a surveillance measure that's presumably quite effective, but also far less invasive than this law and others.