The consequential outcome of joining the service inherently requires the surrendering of potentially giving away your life, which for many becomes a reality, to which only their families can react.
The USA has a mercenary army. This system allows for much of what it does globally, for if the poor didn't enlist for reasons of monetary concern (i.e., those with limited or no other options and those unable to afford college and in need of a scholarship), the army would be far weaker. The USA foreign policy couldn't remain with a draft army, for people would have more invested and, therefore, greater care about global involvement.
What should military personnel be willing to sacrifice? They already sacrifice so much.