A lot of utility companies including Comcast used to not have a flow for “moving” and so you’d get a brand new account with a comcast email every time you moved to a new address. In a lot of cases the techs would just set it up for you as part of the install and give you the password. It’s only in the last 10 years they added anything like that. I have 3 or 4 different obsolete accounts with them where my actual email is the contact email from that time and some of their online systems will reset the wrong password and stuff like that.

One-time logins actually sound useful for things like setting up utilities for a house. Sign up, log in, do whatever you need to do, log out and the account is immediately locked. Nobody expects you to log back in anytime soon, anyway.

If you ever need to interact with the service again, you initiate account recovery using a combination of your contact info and some codes printed on your monthly bill.