Because they’re in the military. People with options don’t join the military no matter what military recruiters tell you.

Why would I join the military for terrible pay, and get shot at, when I could do literally any other job, for more money, I don’t get deployed to ill equipped war zones, I get to go home at the end of every day, and don’t get shot?

You have to be a certain type of person to join the military, and that sort of person is not one prone to introspection.