It doesn't count as giving benefits when one half of the population gets them anyway. That's like having a daughter and a son the same age and telling one she can get a good bed regardless of what she does and the boy that he has to do extra chores or else. Taxes are something everyone gets benefits from, even if they dodge them. Selective service is not. It is not "receiving benefits for signing up", it is "withholding benefits others get regardless of whether or not they sign up, as well as applying punishments, for refusing". There is a difference, much as there is a difference between saying that abortion is legal for any reason until 24 weeks and saying abortion is only legal up to six weeks. One is a choice (in the case of the draft, receiving extra benefits, with no penalties for refusal, would constitute a choice with incentives), the other is merely the illusion of choice. It's like a parent offering a "choice" of activities, neither choice inherently bad, then grounding the child for a month if they choose the wrong one.