I joined up in 1979 for others reasons than just the pay. I was an idealist and wanted to serve out of patriotism. I also wanted to escape memories of childhood I wasn't very proud of. I needed discipline in my life and wanted to be a man. Lesser reasons were seeing the world and accomplishing something in life. I will say that by the end of my enlistment I was making very good money. I was making $905.70 per month as an E-5. In addition, I earned airborne pay, hazardous duty pay, and TDY pay. I actually earned less money once I went to the private sector. Like anything else in life, you have to show initiative and take advantage of opportunities. I knew I could fast track promotion and earn more money if I volunteered for airborne, so that's what I did.Spending some time as a broke Private is just part of the package.
I'll not doubt the patriotism of any servicemember, but let's be honest, here are also many other motives involved when someone chooses to sign up.
The military is often used as a means of bettering oneself, improving one's station in life. Whether as a career or a stepping stone to something else, the benefits are measured in more than just a paycheck.
Training, experience, and that GI Bill have been the draw, not a fat entry level paycheck.