Many countries have (or used to have) similar stored-value cards. They are really useful for some use cases: Given that they are very cash-like (transferable, anonymous unless registered), they are usually available to foreigners and minors without any formalities.

Japan‘s version could at one point even be used to purchase games in Nintendo‘s eStore by tapping a transit card on a game console – genius, given that a big part of their target audience doesn‘t have a credit or debit card.

Yes not only bus or metro, but almost everything. Taiwan put a considerable amount of effort to have a 1 card to rule them all. And it makes life so much easier[1]

[1] https://erickhun.com/posts/taiwan-youbike-bike-sharing/

Isn't this the same as Octopus in HK or FlashPay in Singapore?