Because the purpose of the draft is to provide combat-ready soldiers to fulfill the needs of the army. Only men can do that.
I agree that both men and women should refrain from sex while serving in combat. Of course, that is "judgmental" to the "free-thinkers" and liberals, so that won't fly. 
An expectant father is still physically capable of fulfilling his combat duties. A pregnant woman is not. If she becomes pregnant in a combat zone or on a ship, she has to be transferred out. That leaves a vacancy in that billet, which has a negative impact on the mission of that unit or crew. That puts an extra burden on the remaining soldiers or shipmates.
All the training in the world will not change the relative muscle bulk and upper body strength of a woman to a man. Maybe we should inject the women with steroids so they can bulk up? Ha!
It does in physically demanding combat and rescue roles where stamina, upper body strength, and lifting/carrying ability are crucial.
Now that is a totally sexist statement. You are the one focusing on sexual organs, not me. Any society that depends on women for its military strength rather than its men protecting the women, is a weak nation, and one that is not respected by the rest of the world. That is the kind of military that will lose wars, not win them.
You are so funny. Much of my research was based on reports and anecdotes from other women. It is liberal men who buy into feminist propaganda and whinings.
What does that prove? Just because a woman dresses and looks more like a man doesn't make her as strong as a man.
You seem to have a fixation.
Well, for one thing, men are not yet required to serve. For another thing, wars are not won just by the troops in the front lines. The support services, and the "home fires" are equally important. Someone has to fulfill those roles too. Rosie the Riveter and the Gold Star Mom are just as important as GI Joe.