If you are living in the United States as a citizen, there are some things that you agree to do. There are things you are supposed to obey, which are called laws. You are legally obligated to sign up for draft. If you don't like it, you can renounce your citizenship, and go to another country that doesn't do it. The choice is purely up to you.
In a time of utter national emergency, it is the duty of the citizens of that nation to defend it. Agreeing to do so is one of the fundamental prerequisites to being a member of that society. Whether or not females should also be enrolled on the draft rolls (as is done in Israel) is another debate. Defending one's homeland and fellow citizens is time of war is the basic duty of every citizen - and draft laws are necessary to make sure that, should the nightmare ever come, the nation will be ready for it.
If a large group a nations decided to attack the U.S. or its allies there might not be enough manpower to fight them off. If males weren't enlisted and called to arms then the U.S. could collapse. The enlisted would only be called to duty if it were a dire situation like this. Also, most enlistees aren't forced to the front lines. They could do something in communications or work in a medical facility. There are lots of responsibilities needed that aren't on the front lines.
Honestly, I find it cruelly unethical to push people into harsh, traumatic situations where they may even die--solely on the basis of the sex they were born as. Enough people willingly sign up to fight currently. Sure, some may argue that it's the cost of living in this country, but what's the reason the USA has to do it in the first place?
It is wrong to require every male of a certain age to register for a draft. First of all, Men only is wrong. Secondly, requiring people to fight for a cause they may not believe in is wrong.
Why not establish a voluntary draft registration system open to all genders? Why mandate an archaic get-all-the-poor-men-killed system?
At eighteen years old--heck, at any age--no man should be forced to fight in the army. It's a traumatic experience that could result in PTSD, severe injuries, death, etc., and it is a violation of a man's right to liberty to force them to do so. Encouraging is different from forcing.
It is something nations may should not do. Drafting men only is pretty sexist. The people may also not agree with having themselves or family members put into the military. There are better things to do than fight people from other countries over the quarrels of people with government position.
People are allowed to make choices on most other things in their life, but not whether or not you are going to be giving your life? How does that make sense? If you think that it is worth it to give your life for your country, more power to you.
The USA having a draft is very much a wrong thing. Drafting young men into a war where they could probably die is not a good idea. Anyone that tries to do a draft, unless it is a huge war i.E Ukraine is really not appreciative of human life itself.