There's about a 10 to 1 ratio between non combat and combat roles, and of combat roles less than 1 in 10 of them will actually see combat. The overwhelming majority of the military are people who just want to get a leg up on a career that can support themselves and a family.

That said, I know several people personally that joined up due to lack of options, saw combat, and are now profoundly broken, so I don't mean to belittle that point. Just don't oversimplify things to thinking it's the only thing.