I think it's cultural familiarity and resistance to change. My Japanese wife has no problem booking us tickets and it's been over 20 years since she left Japan -- the interface is probably the same as when she left Japan. People there are used to it and it's good enough for locals so no reason to change (even if it's more difficult for foreigners to use).

When I visited Japan with a friend in an area that's less touristy than other places, I had my wife book my bus/train tickets from the USA since the websites were so hard to navigate and it took a phone call to the bus company to book those tickets - she sent me a note to show at the ticket window to pick up the tickets.

Her mom complains when anything changes, it's been over 2 years since her favorite affinity card switched from in-person redemption to an online app and she still complains about the change.