It's better to create a criminal class by mandating what you do at 20 should preclude you from any opportunity for the rest of your life. No job, no place to live no way out because of one or even a couple of actions. It's hard to imagine that someone was raised in a poor environment and that they go on to mirror that environment . It's better to keep them isolated from successful people that they may choose emulate going forward. It does not always work out but I can guarantee you it's better than having a permanent criminal class.