[TheUnknown]

One Thing I Do Know Is That Some Does It To Ease Their Pain, Like Something They Did Back When They Were Young, Reckless. And They Will Always Hate Themselves For Doing What They Did And So They Inflict Pain To Themselves as a Way To Forget The Pain They Have Inflicted To Others Through Their Actions. So I Guess You Can Say It As a Way of Hating Yourself.

Other Than That, Cutting Yourself Just For Fun Is Just Stupid and I Dont See Why People Would.