I think blanket statements like "they're selfish" just show lack of understanding to an extent. I'm sure we all know extremely selfish people, but they are still around, despite how bad times are/have been in their lives, and then there are people that have never acted selfishly that have killed themselves (of course this works both ways).
My Mum, on the day she died, still went out shopping to pick up the things she said she would, a prescription for my brother, medicine for our pet etc. Yet hours later, she had hung herself, there was no real suicide note, just scribbles on a page with words like "pain" "agony" etc, and the writing was messy, large and almost childlike, nothing like her normal writing. To me this things show me someone that was very sick, not merely selfish. Of course everyone has their own view, but I am one of the people that has been touched by it, and thankfully, most people haven't.
As I said in a previous post, she had suffered seriously with depression, phobia and anxiety for most of her life, and many times she said the ONLY thing that kept her around was her family, so it would appear something just snapped. Unfortunately, we don't know what is or isn't going through someone's head moments before they kill themselves, so I don't think it's fair to label them as something as we simply do not know.