CNBC published an article last Tuesday about how insurance companies (and the government) bill you on emergency room visits. For example, if you go to the ER for a stuffy nose, your health insurance may not cover your visit because it could be treated with over-the-counter remedies. Also, the chance of you actually dying or becoming disabled are very slim from a congested nose. So why do ERs take these patients and run so many expensive tests? Why can't they tell them to go to a 24hr pharmacy and grab NyQuil? Or to follow up with their personal doctor/urgent care?
There are a couple reasons why an ER can't do this from a legal perspective. For one, nose congestion is a symptom of many illnesses, some of them dangerous. If the ER discharged you without running tests, it would be liable if you died from an infection over the next 24 hours. The hospital would risk lawsuits both from the family and the government. At an urgent care, personal doctor, or health clinic doesn't have as much responsibility when it comes to treating you. They have the disclaimer "if you get worse, go to the ER".
Generally though, insurance companies are very good about covering ER visits (and hospitals are good at getting them to cover it too). Insurance companies know their customers aren't always good at determining what an "emergency" is, but they may try and provide more education in the future as costs rise with technological advancements in medicine.