It has been said that everything men do, they do to get attention from women. In our society young men are told they are toxic and 1/3rd of men under 30 got no sex in the last year. Women are just not interested in most men so a lot of them are checking out of our society. I suspect a lot of young men would say that what they have today is not worth fighting for, so why join the military.
I agree with all of this. Men do everything to get vagina. If women aren't rewarding men with their vaginas, what's the point of men doing anything? The military is just one area where men are checking out. A lot of forms of employment are seeing male shortages because men aren't motivated due to being ignored in the sexual marketplace. A lot of blue collar fields have also been affected.
In 1941-1942, a man was motivated to fight in World War II. The USA was attacked by Japan. Also, guys with girlfriends in 1941-1942 were appraciated by their girlfriends and prospective wives. They fought in World War II for America and for their girlfriends. These women in 1941-1942 had a greater sense of loyalty to their men and a sense of commitment. When the war ended, the girlfriends rewarded their men not only with vagina but with emotional devotion.
In the late 1960s, when Vietnam was escalating, the young women of that time weren't as high quality as the young adult women of the late 1930s-1940s. In the late 1960s, the young women were mostly the end of the Silent Generation (1936-1945 births) and maybe the very beginnings of the Boomer generation. These late Silent Generation women were the first women to experience the new paradigm. They were reading Cosmopolitan magazine and using the birth control pill. They didn't feel the same way about their men as the women of 1941. The men recognized the quality decline too. Also, Vietnam was a conflict that the USA didn't need to participate in. There are both liberals and conservatives who see Vietnam that way. However, the sexual marketplace was not nearly as skewed in the Vietnam era as it has been since Vietnam. Women were selling the free love mantra around the time of Vietnam and the men wanted the casual sex of the Vietnam era. However, a good portion of women weren't a part of the whole hippie and Woodstock thing. The average quality woman of 1969 was still ahead of 2019.
The reasons are so many that it gets complicate to list them by hierarchy.
Yes, there are more reasons besides male sexlessness.