I think cash cards here have a life of 3 to 5 years, so banks can change them, add new features and update them. Usually when they are nearing expiry, the banks send out new cards so they can used before the old ones expire. Which is what happened in this case, I just didn't start using it until after old card expired, perhaps because I worry about losing the new card that I use the old one until I can't.
Well there was one time when I didn't get a new card in the post and old one expired unexpectedly (the cash machine spat it out - they only swallow cards if you enter incorrect PIN too many times). I had to call up the bank to get a new one sent, and person said that it was possible that it was intercepted in the post and stolen.