When I was in, we'd come back and would have to see "The Wizard" before we could leave base and all that, he was the dude standing in the way of us and libo, family, booze, women, etc so we just told him everything they wanted to hear. I hope they've done away with that "system."
Other than that, I see travel time back to the world being part of the issue. At sun up you're in Shithole, Wherever, then come sundown you're back in the States. Least WW2 vets had a few month ship back, time to decompress amongst your fellows and all that. As it stands, I'm near a 1:1 ratio of dudes who checked themselves out to dudes we lost in country. I really don't get it.