One of those "things that make you go hmmmm"... I'm driving on I-4 and see a big billboard for Florida Hospital's 60-minute ER. Sounds nice, but why advertise an emergency room? If you're in need of an ER, don't you go to the one that is closest to you? If you get picked up by an ambulance and you're lying in the back bleeding to death, are you asking them to take you to a specific one?
To answer your question ERs advertise for 2 reasons- A. Because someone is going to get that ambulance patient and B. People with insurance are actually more likely to go to emergency room for nonemergency situations than the uninsured. Patients= revenue.