'mmeomo'? You mean emo?
Well there're two possible reasons. Since the emo fad revolves around a vain 'image' of raccoon-striped hair, snakebite piercings and eyeliner, most emos that cut themselves are probably doing it for attnetion.
But those that cut themselves for their own 'benefit' do it so the physical pain they experience overrides the inner, emotional turmoil they experience. Plus, once the pain resides, the chemical your body produces provides a euphoric feeling. So it's similar to why people get baked off their face. To escape reality.
Hope that helped.