The 1 kurus was stopped being manufactured (still have one though:
https://s.ave.zone/969.JPG )
Well, a pound coin is used more than once, and there is tax applied on every time it is used, so it'll pay off for itself in a relatively short timespan, imo. Plus, it pretty much beats counterfeits, so loss from that is gone too.
Problem with 1 kurus was that it wasn't used often, the monetary value was small and that it had no anti-counterfeit stuff. Also, people were melting it and selling it. You can't really sell a broken or write-protected rfid chip for much.