They are going away soon (TM), the tech is cool but they are impractical. I will be happy to use my credit card or phone. Too many times I have been stuck in 15-20 minutes queues to buy those tickets and you cant refill them with an app... Plus south shore and north shore have they own system it's a mess.
- Full offline support (i.e. both the reader and payment device don't need network connectivity), making the system more resilient
- Symmetric cryptography and highly optimized transaction flow, making reads more reliable and allowing faster customer flows through transit gates
- Upfront transparency about charges, monthly passes, capping etc. – you immediately see your balance left after tapping.
- No "transaction spam". This is more on my specific transit provider (NYC MTA), but I'm really not a fan of getting an individual credit card charge for every. single. tap. It can't be cheap in terms of fees for the operator either! At least other systems, like TfL in London, aggregate taps over a day, but it's still not great.
Singapore's public transit agency recently attempted to switch from a stored value based model to an exclusively account based one, but had to backpedal quickly due to public outrage about the move.
Ideally, a system supports both payment methods: Open-loop payment cards for infrequent users, and stored-value cards (both physical and in digital wallets) for heavy users and anybody else that prefers them. But realistically, maintaining both is too much of a burden for many transit agencies.