They don't have license plates, they have mandatory registration stickers. You can't read it unless you look closely at the sticker while the bike is stopped. It's to identify owners of stolen bikes, not identifying running bikes.
To be clear, when the OP wrote "Japan has bicycles with license plates", it is important to clarify the term "bicycle". It would more accurate to say "motorized bicycle". If you ride something that looks like a bicycle where you can power it only with a throttle button (no pedalling required), then it requires a license plate, at least in Tokyo. Explanation here: https://www.city.inagi.tokyo.jp/en/kurashi/zeikin/1002693/10...
Also, you can ask Google AI for more sources and info using this prompt:
To be clear, when the OP wrote "Japan has bicycles with license plates", it is important to clarify the term "bicycle". It would more accurate to say "motorized bicycle". If you ride something that looks like a bicycle where you can power it only with a throttle button (no pedalling required), then it requires a license plate, at least in Tokyo. Explanation here: https://www.city.inagi.tokyo.jp/en/kurashi/zeikin/1002693/10...
Also, you can ask Google AI for more sources and info using this prompt: