Suicide, self harm, and depression are all really difficult to discuss. The initial point @
primitive made is valid, but people committing or considering suicide are usually consumed by some mental illness (depression, anxiety, etc..), thus their thoughts turn to helping themselves via death or cutting, not really pausing to think about what they're doing. It's not that they're being selfish, it's the fact that they literally can't think of anything else.
Edit: I also try to avoid discussion about depression, as a friend of mine killed himself in october, my ex-girlfriend nearly killed herself in 7th grade, and I was facing depression for the better part of my early teens.
It's often the outcasts, the iconoclasts ... those who have the least to lose because they
don't have much in the first place, who feel the new currents and ride them the farthest.