If I may ...
I've often wondered that myself. Why is it, that a "hospital" is incapable of treating a trauma or heart attack patient? Do they just do the real easy medical stuff and charge outrageously high prices? Can't nearby hospitals at least stabilize a patient and then, if necessary, call for transport?
The entire range of more highly trained staff, from doctors through nurses and technicians, as well as the massive array of specialized equipment, is what makes shock trauma units and ICUs something that not every hospital could ever possibly maintain.
When I fell off the roof of a building, they flew me to the UM-Baltimore shock trauma unit, considered one of the best in the entire country. They barely managed to save my life, initially, and then miraculously managed to save the use of my legs. because the orthopedic docs supporting that trauma facility were the best of the best and had all sorts of cool experimental stuff they tried on me (that worked...I'm the subject of some papers in some medical journal somewhere...LOL). A regular hospital like Calvert or St. Mary's could have done none of those things...I'd be dead, or, at best, in a wheel chair for life.
When my wife broke her leg in 12 places in a horse riding accident, they flew her to the trauma center and Prince George's Hospital Center. She went through a series of operations conducted by two very remarkably talented ortho surgeons and they save her leg...just barely. Again..nothing that could have been done locally.
One of my best friend's sons and some buddy's were horsing around with a "short bus" they bought as a joke to have some fun with. The boy fell out of the bus door while it was rolling and cracked his head really hard on the pavement...massive concussion and brain injury. They took him to St. Mary's. When my buddy arrived to see his son, the staff had just called in a priest to administer last rites. My buddy went apeshit ballistic on them and managed to get an emergency transfer to Georgetown underway. That young lad survived...and stopped by my shop today about some motorcycle repair work, in fact. It did take several years of continuous rehab before he regained the use of most of his faculties..but today you'd never know that the St. Mary's hospital had given him up for dead.