[Fat Charlie]

It looks more like they've been in the rut so long that in their minds the ER is "the doctor's office." Only someone completely ignorant would willingly go to the ER for something that a walk-in could handle, no matter who pays for it.

Then you can look at factors like ERs being open at night and easier to get to, another part of the rut these people have been in: they know where the hospital is and they've never been to any of the many urgent care clinics in the area. Simply offering to cover medical bills doesn't change enough of what's wrong in someone's life to make it a good experiment.