3 things.
#1 it’s harder for the system to have fare groups (ie. discount, monthly)
#2 with no stored value it’s hard for the system to understand where and when a card has already been used. ie. if you tap on with your credit card but then transfer it can’t know you paid your fare at last tap
#3. Transit doesn’t get enough valuable customer usage data
The key with the transit specific card is that it keeps data right onboard.
Oh it’s the last one then. I only ever use a credit card on the mainland, tap on and tap off when required.