Actually, one of the most interesting questions about any scenario in which the draft were activated is how selective the military would be in terms of physical fitness. It's not difficult to imagine them rejecting something like two-thirds of those whose numbers come up, especially if they widen the draft pool by including women. Most Americans, even in their early twenties, do not meet the military's definition of fit for service.
According to an MI ANG app I almost started filling out, more than 15 uses of marijuana renders one permanently ineligible for military service, so honest people would also be disqualified.
