You can pay a GBP5 "deposit", which is inconvenient to get back without registering, but cash top-ups are available from machines and ticket offices under certa

You can pay a GBP5 "deposit", which is inconvenient to get back without registering, but cash top-ups are available from machines and ticket offices under certain circumstances. Also, like with most things these days, we're sold on the convenience that registering adds i.e. no loss of funds if lost or stolen, and "auto top up" from your registered credit / debit card... most people don't care enough to pay an extra GBP5 to make their transport history "disappear" every so often - especially when there are so many other ways we're tracked.