Self-cutting could actually form an addiction, just like drugs do. And like drugs, it gets people high. Self-harming releases endorphins that our body enjoys and yearns so much for.
Some people start it because their friend do so, and since everyone else is doing it, one might as well give it a try instead of getting kicked out of the group. Some started initially to punish themselves, they are angry at their own life and failure, and cutting gives them that distraction away from the emotional pain, directing it to physical pain.
The brain eventually develops a tolerance to it and requires you to cut yourself more and more. What started as a coping mechanism slowly turns into a life ruining addiction. Similarly like drugs, trying to quit gives withdrawal symptoms and makes quitting so much harder. It’s a compulsive behavior that is difficult to stop once hooked.
My suggestion is don’t ever start to think about trying, and if you found your friends addicted to cutting, they need your help.