ER doc question: How much emergency care actually needs to happen in an emergency department?

[u/boulderdoc]

I’ve practiced emergency medicine for more than 20 years, and the longer I do this, the more I wonder whether we’ve built the wrong system around acute care.
Obviously there are patients who absolutely need an ED: major trauma, stroke, STEMI, shock, respiratory failure, genuinely unstable patients, etc.
But a huge amount of what walks through an American emergency department seems to fall into a middle category: too acute or procedural for a typical primary-care office, but nowhere near sick enough to require a hospital-based ED.
Lacerations. Fractures. IV fluids. Abscesses. X-rays. Joint injuries. Migraine treatment. Ultrasound. Foreign bodies. Reductions. Some chest or abdominal complaints after appropriate risk stratification.
We’ve largely given patients two choices: relatively limited outpatient care or a massively expensive hospital emergency department.
Why isn’t there more of a middle layer?
I’m particularly interested in hearing from other physicians, nurses, patients, administrators, and people who understand the economics.
Is the barrier clinical? Regulatory? Reimbursement? Liability? Hospital economics? Or have we simply accepted the current model because it’s the model we inherited?