Two of my takes on the subject:
- the draft dates to the days when wars were fought between states with defined battlefields and masses of troops. (See the Revolution, Civil War, WWI and II, Korea.) Even in Vietnam the fight in the later years was between uniformed forces as North Korea fed their regulars into battle. I strongly doubt we're going to see many of those wars in the future. Iraq had one of the strongest armies in the world, and it took 100 hours to defeat it in 1991. So the draft is pointless militarily.
- the draft is a strong symbol of obligation to the nation. All are equally obligated, so women should be required to register.