We're told a lot of things by "officials" not because it's correct, but because it holds the least legal liability for official parties involved, especially anything involving healthcare. These officials also sometimes include doctors, who work to protect themselves and the system first, and then patients.
Asking a lay person to know what a BLS (non-EMT fire & police), EMT (Ambulance), Parmedic, or MSO can take care of, or even what the differences are, is, I don't think, super useful. The red vehicle shows up and takes you to care.
In the case of MCI, EMTs can a) give aspirin or nitro (rx), b) have an AED and lots of CPR training but have to stop the vehicle to give effective compressions, c) a radio and the ability to meet up with Paramedics.
Paramedics have more complex treatments (drugs) and EKGs, but it's still 2 folks in a truck, not a hospital. They can do amazing things.
But as the joke goes, sometimes the best treatment is High Volume Diesel Therapy (burn rubber).