Quite a few of my university friends went off to join the military-industrial-circus and I saw their rationale for doing so change over time. Initially something like having learned the ADA programming language coupled with a poor degree result meant that 'defence' was the only option open to them unless they wanted to stack shelves at a supermarket. Then the family came along, with the mortgage and the responsibilities of being a mature adult. The rationale shifted, working for the military machine was now just a means to an end, for bread on the table, where there are bills to pay. This is what happens.
Initially they went to work in the defence industry because it was their only option unless they wanted to stack shelves.
Later they continued working in the defence industry because it was their only option to put bread on the table and pay the mortgage.
Those both look to me like "I'm doing it because it's the only option I have that uses my skills to do something that pays decently".
What I'd find more interesting would be if people tended to shift (1) from "I do this because I think it is a noble way to serve my country" to "I do this even though it's horrible because the alternative is poverty" or (2) from "I do this because the alternative is poverty" to "actually it turns out that this is a noble way to serve my country".
