As someone who has spent many years working in defense / government contracting, I think you're touching on a really big reason a lot of people work in this world.
Many years ago, when my career first started, I was an idealist who thought the way I could give back (as someone who couldn't get into the military for physical reasons) was to work in the defense sector. I also tried very hard to get interviewed by an SV company, but I didn't qualify for an interview due to going to the wrong college and getting the wrong degree.
And I have worked on some seriously badass programs and with some really cool systems and people. In my older age, it's funny because I've come full circle. I'm actually using my experience, and the new all-remote world, to interview with some tech companies. I'm also starting to sour a lot on working with the government and military because my idea of "giving back" has become much more cynical. EDIT- I meant to say here that I've become much more cynical, and working with the government no longer feels like "giving back." Nowadays I give back by working on social issues.
BTW, I'm also upvoting / interacting with your comment because (a) I think you're getting downvoted by people who disagree with you, rather than by people who think you've broken some rule, and (b) I think your perspective represents a pretty common way of looking at SV from the outside world.