- Religion says that you will be tortured after you die. Suicide is a sin, something you "commit".
- Should you be partially successful, doctors will keep you alive in a kind of living hell. (I have had this threat made to me.)
- The only readily available forms of suicide are painful.
- Life is worth living.
Our society relies on the first three. This is un-ethical, and if one is keeping someone else alive for one's own continued ease of mind, selfish. "We couldn't be bothered making your life worth living, but we'll force you to go on living anyway." Thanks, asshole. Guess what advice I'll be giving your doctor when you have a painful terminal illness: "Do anything it takes to keep them alive, doctor. Anything."
This vindictive, tit-for-tat strategy is ethically justified according to Peter Singer. I like it when feelings and ethics concur. <disturbed grin>
Still, suicide isn't too hard if one is determined. Why do most people not attempt it? Peter Singer quotes Albert Camus as saying "Judging whether or not life is worth living amounts to answering the fundamental question of philosophy", with suicide the logical consequence of judging life not worth living. So, from available empirical evidence, most people judge life worthwhile.
A related question is whether or not to have children. If the species homo sapiens is a bad thing, it is not worth making more of them, yet many people are quite willing to do so.
There's one glaring exception, rich Western democracies. Suicide rate up. Population growth down. Good for the planet. It's a suicide ethic.
This applies especially to "left wing" liberal thinking. In abandoning traditional moral codes, we also gave up the traditional purposes ascribed to living, such as growing strong and tall to be ready for God's harvest. And we focus on the bad things people do, so that it seems our species is bad overall, and mere selfishness prevents us from performing mass suicide.
The resurgence of the right is a backlash against the suicide ethic. This is why abortion is an issue again: abortion means less children, and the traditional religious view is that having children is a good thing. Similarly gay marriages produce less children than straight marriages, on average.
A poor solution, yet where is our alternative? The best purpose Peter Singer can imagine, in his book "How are we to live?", is to reduce suffering. He is unusual for considering the question at all. Life is worthwhile, why can't we say so?