I understand what you're saying about suicide being a selfish act because all the people around them are the ones left to suffer. But I don't think you're seeing the bigger picture.
When I was about 15, a mate of mine killed himself. It came totally unexpected and was a shattering blow to everyone, even those who weren't that close to him, because he seemed like a happy person, who had a lot going in life, and who was quite popular....I guess not!
After his death, I worked with a suicide crisis centre, as part of my healing process (i needed to understand what he was feeling/thinking and why he felt he couldn't speak about it), what I realised was people who are suicidal want to die because they believe it would be better for everyone if they never existed. Different circumstances cause this belief, but the thought that they're death would make other peoples lives that much better is so strong that it forms tunnel vision.
I've never tried to kill myself, but I've had periods were I've thought that may be this world doesn't need me. And when I've thought this way, the last thing going through my mind is how selfish i'm being.
If you asked someone who thought like this, what the'yre thoughts were at the time, guranteed they'ed say their doing you a favour!
You might view suicide as a selfish act, and I strongly disagree with people who act suicidal just for attention, to me that is selfish, but truely suicide isn't selfish it's just a state of mind, and until you've been there, be it directly or indirectly, you don't really know!