Yes, this is a hard one and I've thought a lot about it. I think our reasons for wanting to prevent suicides come down to evolution: it's bad for us if people around us are killing themselves. We will do anything and everything to ensure that unhappy people keep on livin'.
I think the more humane approach is to damp suicides to some extent, but to have a respectful mechanism that allows people who have thought it through to check out when they please.
The fact that we have laws preventing assisted suicide is beyond me.
My wife has a condition where she will be wishing to commit suicide someday. Our country (France) law makes it near impossible. Then we have Switzerland, Belgium and the Netherlands nearby where this will be possible.
Net effect? People like us who have the knowledge and money means will get suicide. Others will not, making their family or community life even more difficult.
This was exactly the case with abortion in France until the 70's (and Mrs Veil who was one of the not do many politicians in the last 100 years who was great). I guess we will be always late with history.
I think the more humane approach is to damp suicides to some extent, but to have a respectful mechanism that allows people who have thought it through to check out when they please.