In those days it was enlist, or be drafted in many cases. My father enlisted at age 17, into the Marine Corps.
I personally believe we are a better society, with more veterans in the mix.
During WWII our population was 160 million and 10% served in uniform.
Figuring few women served, and 1/2 of population are men, then the 16 million that served made up nearly 20% of the population.