My wife and I share passwords fairly regularly. Usually in a context where one of us is busy and wants the other to log into something they set up (e.g. to pay a bill), so the entire point is to not spend a few minutes going through an enrollment flow or whatever to give the other access (otherwise they'd just do the task). We may also not be in the same location when things like that come up.

Tying a credential to a single human is exactly not something desirable for a subset of users. Some married couples essentially act as a single person in most contexts (e.g. sharing an email address and/or phone number), which kind of makes sense; legally (in many states) the point of getting married is that everything becomes shared. The goal is to reduce friction around who owns/has access to what.

The real world obviously has different constraints, but works basically in this way. e.g. if I go to drop off/pick up a prescription for my wife, I just tell them her name, not mine. We use credit cards with the other's name all the time. etc.

> What's your proposal on what a better UX might look like (along with getting everyone to adopt it)?

Passwords, obviously.