I think people leave the field because:
(1) It's inherrently stressful. Some of this stress can be mitigated by having better management, better pay / working conditions -- but ultimately doing EMS means exposing yourself to a certain type of horror, like the occasional pediatric cardiac arrest. Some people realise they've had enough of this.
(2) There's a lack of lateral movement. Once you work as a paramedic / EMT, you're pretty much committed to working on an ambulance (or maybe, a fixed wing or helicopter). There's relatively few management positions, clinical education positions, in-hospital positions, etc. They exist -- but it's not like being an RN, where if you get tired of the ER, you can work the neuro ICU, or take a job in case room, or public health.
(3) Back injuries are rampant. A medic / EMT who can't lift is going to have a very hard time finding work. This is partly because we (like the general population) don't take care of ourselves. It's also because we do a lot of awkward lifts.
(4) Shift work, and emergency services, wreak havoc on family life. It's hard to understand why your spouse is so moody on a Friday, if you haven't worked a monday-friday schedule in 10 years. It's hard to keep track of time passing when you have an abrupt reset at the end of the last night shift of each tour. You see things that you often can't share with your spouse, either because it will upset them, or because they won't be able to understand. There's plenty of upset, stressed out people in EMS, and marriage-ending infidelity is extremely prevalent.
(5) Pay is a factor in some regions. Personally, I didn't find it a problem -- but I think I was quite well paid as far as paramedics go. A new medic in the service I was in probably makes about $65,000 - 70,000 a year right now, if you include training hours, early/late trips. But it was a problem early in my career when I was doing 24 hour EMT shifts in rural nowhere for $70/day (6on/3off).
My experience was very much that people left at the beginning, in the first five years, as they realised how poor the working conditions were for EMTs in all but the marquee, unionised services, that were primarily looking for paramedics, or 1001 Firefighter-EMTs. When you train enough people to EMT level each year to fill every available 911 spot in the region -- it's natural that a lot of those people won't find work. It seemed like there were a lot of younger people who moved on with a couple of years of their medic -- as they realised that being a paramedic doesn't suddenly change the nature of the job. You have more responsibility, more interventions, more change to do good and to do harm. But the same social problems and system problems exist at every level.
A lot of the female EMTs/medics would leave after having kids. Trying to find daycare for an EMS worker's kids is hard. You never know when you're coming home. The shift might end at 1700. But you might not walk in the door until 2000. Your 14 hour night shift, might just become 18 hours with some bad luck and the wrath of the SSM gods.
Myself, I actually miss EMS. I felt I got good pay. I felt I had healthy coping mechanisms. Had I gone to medical school when I was 22, things might have been different -- but now, I'm not sure the cost/benefit works out. Helping people is a fundamentally decent thing. That's what EMS is about; fixing problems and helping people. While I didn't feel that my management respected me, and sometimes it depending on the RN and the MD and the given night, I wasn't always sure whether the hospital did. I was never quite certain that the community really valued what I did. But I thought it was worthwhile. I thought it was something to be proud of.
I disagree, by the way, that if one wants to talk about medicine, one should go to medical school. I would agree that if you want to be a medical expert, this, or selected clinically-focused lines of research, are the two pathways. But I don't believe it's wrong for a paramedic to want to talk medicine. The best physicians I have worked with have always encouraged this. There just needs to be a realisation that we are physician-extenders, not physicians. We treat disease in the community in situations where it's not possible/desirable/cost-effective to have a physician present. We move people between the site of their injury/disease process and the hospital, or between two different facilities. That's ok. That's a unique competency within medicine.
One of the better parts of being in EMS, for me, was feeling that I was helping build something better. I admit, I didn't feel like this every day. But on the good days, I felt like I was a very small part, of creating something very important.
All the best.
