I can't see any legitimate technical reason to restrict passwords. In my example, they could put a sensible account system on the front end, and do whatever th

I can't see any legitimate technical reason to restrict passwords. In my example, they could put a sensible account system on the front end, and do whatever they need to in the back end to link it to my phone number and a random 8 digit number, if that's what they need. Same with banks. They can set up a real user name and password from you, store it in a modern system, and link it to the older system behind the scenes. Perhaps there's some arcane legislation that prevents this, but it seems unlikely.