To illustrate my point:
When a large group of young people die in wartime, their deaths have implications on the future population. Not only will these men never become fathers, but the women they would have married will never become mothers. Uneven gender balances are very dangerous, and led to
a population crash in Germany after WW2.
If you send both young men and young women off to die, their deaths "counterbalance" each other. Because there is still an even gender ratio, more families will be formed than if only men were drafted. The population won't shrink very much.
Some environmental activists want our population to shrink, but in a service economy
population shrinkage leads to GDP shrinkage. If our GDP begins to shrink, our economy will tank. This would be really bad, and probably more dangerous than the deaths of our soldiers overseas.
We also live in a globalized world and (assuming you're in the US) within the most militarized nation in the world. I appreciate contingency plans but the draft as we know it (ala Vietnam (which was an offensive war, not an existential crisis)) seems very irrelevant and outdated in how both modern society and modern military operates.
You're probably right, but if the US is ever brought into a land conflict with China, the number of troops deployed will be pretty significant. China's population is what political scientists like to call "fucking massive", as they can easily arm tens of millions of young men and women at a very low economic and social cost. Because the United States will not be able to compete with China's numbers, and because our allies have smaller militaries than we do, a draft may actually be necessary to stand a fighting chance.