I think there are at least some studies that show one aspect of well-being is feeling like you are a valued member of your society. You can be a relatively poor grandparent who is valued by your contributions to your family, or a volunteer, or whatever. I think for many a job becomes a unconscious proxy. You could probably also study people who are paid well, but in jobs that society doesn't generally hold in high-esteem. My mind goes to attorneys who have enough well-being issues that the American Bar Association issued a task force on well-being. I would venture a similar issue is what causes some veterans to struggle when they return to civilian life.

I guess what I'm trying to say is that a job is just a useful proxy for measuring how people feel they are contributing to society, but it's an imperfect one.