There's a huge difference across the services when you compare everything, SF 18Ds, Air Force PJs, Independent Duty Corpsmen...a civilian EMT in a progressive EMS probably has more training than a 68W.
It also limits what they are able to do when they get out, very few want to go through a year long Paramedic program or bridge to RN or PA.
I've worked with and hired some guys who were in and transitioned to the civilian side, some did really well, others not so much...had no concept about the medical side of things, if I've only got 7 weeks to train you, Im not going to teach you about complex disease processes like Heart Failure or Cardiology when you aren't going to see those in generally a healthy group of people.
It's a disservice to them, would enhance the skill and training while you were in, and give you a skill set that would transfer to the civilian side when you get out....
There has been a huge evolution in "cross-credentialing" military medical providers when they get out. UNC-G has a military medical provider-to-BSN program; Congress has the Veteran EMT Act. More states are acting on it. I forsaw it going downhill when IDC stopped transferring credit to PA school and 18D stopped issuing NR certs.
I agree that most 'basic' military medical providers are heavily-invested in singular areas; trauma, and rightfully so. A FMF corpsman or 68W has, on the average, far more real-life trauma and mascal experience than civilian medics. I can't speak to 68W, but for FMF corpsman I was also part preventive med tech, part dentist, part advanced provider (suturing, chest tubes, blood admin, advanced diagnostics), but most of that is battalion surgeon-driven.
But with casevac, if you are going to transport patients from across the continuum, they need to meet the standard (EMT-P, CCP, FP). Pedro in Cherry Point went belly up, but Camp Lejeune still transports patients to civilian hospitals, with a corpsman and a nurse they just grab at random (may or may not be a Navy nurse).
Pararescue is an island unto itself because it has a mission tasking of civilian SAR so EMT-P is the ground floor credential (then they add DMT, others).
Historically in the Navy there has been no standard with flight medicine. When I joined I was already a EMT-P/CCP with critical care transport experience; they sent me to Cherry Point for helo dunker, aeromed physiology, and water survival, and I was instant flight corpsman and SMT. When I got my commission they were sending corpsman to Ft Rucker to the Army's program but it was always a sputtering, start-and-stop thing for the Navy. The Marines have committed a plan for organic flight transport (historically never had it), but the Navy (BUMED and NOMI) never really bought into it.