Honestly it would never even occur to me to call my ISP to help if I'd forgotten my wifi password.
Also I feel like if you are concerned about forgetting your wifi password you'd probably just keep the one that's written on the device (and which is probably quite a bit more secure than the password you'd come up with yourself).
Xfinity these days will have the tech set up your WiFi with your password. It's an integrated device so he'll set up the cable internet and then your WiFi. Monkeybrains is all "you're set up!" and then you add your own WiFi router. Sonic has you set up your own WiFi. AT&T has the WiFi password printed on the device along with the admin password.
That's my experience with ISPs in SF. It's clear that many people don't buy Internet access. They buy "WiFi" which is that Xfinity integrated service. The components don't matter.
I'm certain that nearly most, if not all users on hacker news have a pretty solid mental model of the basics of how internet connection works, and the responsibilities between the computer or device, wifi, home router, ISP, and internet web sites or other services.
But I've assisted people who's mental model is simply "Verizon put this box in my home and now I have internet". Who panic when a site doesn't load, and will call the first person they think is responsible for the problem. (typically, the company that gave them internet). Or more commonly nowadays, "my phone is my internet connection" -- and the only thing they think they have the power to do is to wave the phone in the air to find 'more bars'.
I suppose it makes sense from Verizon's (or any ISPs) perspective, and honesty, if you understand how all this works, then you understand how to trivially eliminate the issue, and then of course, you know when and when not to call Verizon with problems. (Of course, it'd be awful nice if they offered 'Shibboleet' [1] service for folks who do undertsand when the problem is between the site and the router.) HOWEVER, it'd be nice if they were more upfront with the disclosure of this password sharing ...
Also I feel like if you are concerned about forgetting your wifi password you'd probably just keep the one that's written on the device (and which is probably quite a bit more secure than the password you'd come up with yourself).