Unfortunately for many senior folks, using them is just too complicated. I've badgered my parents into using theirs, which is already setup, and it confuses them every time, so they prefer to memorize or write their passwords on a sheet of paper they never lose in their apartment.
It's just easier than fiddling with a buggy mess of auto-fill prompts that only work half the time, and when they do show up, they fail to fill in the password, so then you have to open the app, hunt down the entry, copy it to the clipboard, and go back to the app or site you were signing into.
Multi-tasking on phones is already very difficult for my parents, and they're well aware of it being a feature. Eventually all of these frustrations add up, and the path of least resistance is writing passwords down, as much as it kills me.
- It's always up to date
- Previous values are kept (but hidden)
- It encourages stronger passwords
- Its automation makes it harder for people to put passwords into the wrong/phishing sites.
- You can share passwords across a group
- Remote administration
- Distributed possession: You have them on your phone out and about, you have them at your desk.
Really, a password manager is a really great tool. I don't know your family but I strongly recommend using and supporting one.