In other words, it's a tragedy of the commons situation.

Nobody except a few crazies want to sign up for military knowing they'll likely die and if nobody signs up then all will die; volunteer army is almost entirely people who don't actually expect to die.

The most sensible choice for an individual is to avoid the military and that's why conscription is needed or the country is lost.

In other words, it's a tragedy of the commons situation.

Nobody except a few crazies want to sign up for military knowing they'll likely die and if nobody signs up then all will die; voluntary army is almost entirely people who don't actually expect to die.

If your country doesn't need conscription it's not actually at risk and if your country is actually at risk it needs conscription.