This is maybe the one and only thing that’s not exaggerated in movies. In real life, it’s even worse. One thing every recruit in basic training has to pick up quickly is the “military speak”. The military slang is something every recruit learns quickly. It is a way of distinguishing between “us” and “them”, and also to create sense of belonging.
When I joined the German army, it surprised me how different the military terms were from what I’ve seen in the movies and read in novels. The barrel is called ”Rohr” and not “Lauf” as they say in the movies, and you say “gleiten” (gliding) instead of “kriechen” (crawling).
Some acronyms can have different meanings in another language. The acronym for the German Army’s Military Air Traffic Control, the “Militärische Flugsicherung” is MILF.
Additionally, every unit comes up with its own informal terminology. A new recruit, for example, was called a “Koffer” (suitcase) in my first unit, but “Muschi” (pussy) in my second one. They called them “suitcases” because in the first week, their name tags weren’t ready yet and the recruit had to wear a provisory name tag, like the ones you put on your luggage.
In the US Army, it’s even worse. The Americans love their acronyms. The term “Hummer”, or “Humvee”, for example, comes from the acronym HMMWV which stands for “High Mobility Multi-purpose Wheeled Vehicle”. Only in America! So I will say that military members (not just Soldiers) use military terms. While it’s no longer literally beaten into us, it is required that while in the military that we use military terms. For example, “Head” for a bathroom, “scuttlebutt” for a drinking fountain, etc.
Once we get out, you might think that we’d do away with it. And that might be true for someone who’s spent a single enlistment (or even two), but for the rest of us, it’s ingrained. I still say “Roger” when my supervisor gives me instructions. I still use “very respectfully” when I sign my emails (vs “thanks – which in my opinion, is unprofessional in the extreme – regardless of having been in the military), and I still shine my boots. (As an aside, I still wear steel toe. Given how often people burst through the door of the head, I’ve found that it’s a good idea to wear steel toe boots to prevent actual damage).
For a lot of people who did extended bits in the military, the military was how they learned about adult life. It’s hard to divorce that from the civilian portion once a member has left the military and re-joined the civilian workforce. This, of course, is not even considering PTSD.
And of course, you can’t forget about Israel. I’d like to give a bit of a different angle on this question. My friend lives in a different country that has a bit of a different culture regarding this. For people living in Israel, army slang is used occasionally by just about everyone. It doesn’t matter if someone is in high school, after the army or a senior at work. It is pretty much ingrained in the way we speak, for some more than others, though.
The nature of the way they grow up, where everyone (including women) start getting ready to serve in the army in the middle of high school, means that all Israelians are all exposed to army slang (amongst everything else) very early.