How can this actually work?

An ER/ED (emergency room/department) is part of any hospital. It serves two purposes 1) You WILL die unless you get immediate care 2) You might need to be admitted but your doctors can't see you in a timely manner.

This was a situation for me. I went to the ED at a hospital in my network and left before signing in. Why? The wait time was 20 HOURS! I don't see how emergency care is possible when you have to wait 20 hours to get seen. Plus unlike a doctor, you can't set up an ED appointment. You have to be there the entire time.

Instead I went to an out of network Urgent Care facility, but if it was an emergency rather than possible hospitalization before 2 weeks from now, I might have died.

Updates
+1 y
Since I seem to need care only when my doctors aren't available, I am considering concierge medicine and just having my pulmonologist (my only specialist) just admit me when necessary.
How can this actually work?
Post Opinion