I think it made me more mature, or at least less naive about certain things...eventually. The experiences were valuable but it took a long time for me to fully reflect on them and extract that value. I was 22 when I got out, barely past being a teenager.

Money wasn't a factor for me. I had 96% of my tuition to a good engineering school paid for by scholarships, which I gave up to enlist. My reasons were a combination of things. I had a lot of friends who enlisted and I felt bad that they were risking their lives and I wasn't. I was also sick of school and saw war as an adventurous alternative, and a way to prove myself as a man. And I genuinely believed in the mission at the time.

I think the influence of money on soldiers going into actual combat is overstated. It's true that there are a lot of people who enlist for a paycheck, vocational training, or as a way to pay for college. But you get to choose your job. I was in the infantry, and pretty much everyone I knew legitimately wanted to fight, which is the only reason to join the infantry. If you're after job security or education benefits, you can be a clerk or a mechanic or a thousand other things that will generally keep you away from enemy fire. There's an idea floating around that the government keeps people poor so it'll have an endless supply of desperate peasants to feed into the meat grinder, but that doesn't hold up in my experience.