When a whole society is made to be slaves that is not beneficial to society as a whole, nor the individual. Korea has some of the highest rates of depression and suicide.
Very few states are using conscription to expand their borders. It's usually just a way to reduce official government spending and because young males are affected people at large don't care anyway.
Israel has even worse requirements for military service and of course they have at large failed to expand their borders
A big reason for why we see this is that wars become very costly politically when you have conscription. The US government can get away with having an aggtressive foreign policy since people are not forced to participate (other than paying taxes which are not generally higher than other countries).
There isn't any justification for this, if women don't have to serve than neither should men.
Why shouldn't we discriminate based on sex-characteristics?
In the modern era, what has pushed things closer to conflict and invasion is military upbuilding and the lack of understanding others.
The ukraine conflict is a clear exception, putin decided to invade to expand the borders of russia and he was willing to pay a very high price for that. This is a return to the historic norm.
Also, South Korea's own government is invading them in this case by taking away their rights and restricting their internet, so that invasion into people's lives is what needs to be fought.
It's a mistake to conflate what's good for the state with what's good for individuals who are governed by the state.
Also, a single military jet can cost over 70 million dollars.
That's actually cheap.
Medicare is the second largest program in the federal budget: 2022 Medicare expenditures, net of offsetting receipts, totalled $767 billion — representing 13 percent of total federal spending.
1% of that can buy you 100 fighter jets.
https://www.pgpf.org/budget-basics/medicare
Taxes are to a large extent wasted on the elderly (the least important members of society) military spending isn't the problem.
2 million used into teaching people to go onto Instagram and get to know others and spread messages of peace would be far more effective, as well as ending all sanctions against North Korea and the ending of censoring North Korea sites.
Appeasement has been tried in the past and it hasn't worked.
This risk has always been decreasing and it's usually only push towards military that makes it more likely to happen.
When there are 2 competing states war will happen at some point unless they agree to marge peacefully.
Almost all the terrorist acts committed against the United States were due to United States military intervention in the Middle East.
You didn't provide a citation for this.
The US became a lot more aggressive post 9/11 and the tragedy didn't repeat.
It is very inefficient and from the perspective of having a defense force it doesn't even make much sense as people forced to do something won't be well trained. Better defense would come from giving all citizens first amendment rights, but South Korea has very harsh gun laws as do most countries who practice conscription. Basic military training is unlikely to benefit many other aspects and most of the time just interferes with students trying to get careers or go to university. In the United States 1/3 of homeless are veterans.
For general weapon training to make sense people do need to be able to quickly get hold of the weapons needed to defend against some attack.
Just giving access to basic weapons like an AR15 probably isn't going to be very effective against an advanced military. For example you can attack with artillery (from a great distance) or bomb cities from the air.