I've thought about suicide a lot. Not so much doing it, though I have sometimes felt so bored of life that I've thought I may as well, but about why I or anyone else would do it. When I've felt particularly bored of life - same ol shit, different day - I've essentially ended up chastising myself for being unimaginative or just downright lazy.
Once someone contemplates suicide they essentially stop placing value on life, and when that happens the person is liberated to do anything. A lone suicide means that the person values the life of others - they didn't use the terrible strength and freedom of that decision to go postal on their boss etc - and so from their lonely death arises the realisation of a value that may have justified their existence.
I don't feel that value. I don't believe there is a god or any sort of afterlife/reincarnation punishment. I believe that we are animals with instincts and when we die we cease to exist. I don't believe in morals (right and wrong) but I do believe in a... malleable... sort of ethics - how to live your life. I may not instinctively find worth in the lives of others but I would not have a better life myself if I showed this to the recurring characters in this drama we call life.