Earlier quoted context omitted.
"Today in the US, if you call 911 about an emergency medical condition, they will often send a fire engine along with an ambulance [...]" This is SOP (Standard Operating Procedure). 1. Imagine a scenario where an ambulance arrives as a first responder, and the EMTs [1] find that they cannot gain access to the emergency scene, because the home or other structure is locked or otherwise blocked. In this case, a firetruc…
And yet I can imagine this is something that could be optimized; why not cross-train the three emergency respondent department members into jack-of-all-trades that can deal with 80% of cases? Or put members of the three departments into a single vehicle equipped to deal with most cases? They could travel swifly to the site and deal with most cases, and call in back-up (like a fully equipped ambulance, fire-truck, or…
Because we need firefighters anyway, and EMT's in ambulances are often volunteers or paid substantially lower than a fireman in most areas of the country. Bear in mind, you're also talking about putting additional equipment in what is already a jam-packed ambulance, if you end up needing to dispatch another vehicle it might as well be a fire-truck (you never know when someone forgot to say "my house is on fire" when they called in because their wife isn't breathing after dragging her out of the house).