This is a very complicated issue that cannot be done justice with a simply answer.

That being said, I'll bring up a few points and we'll get this discussion going:

1) Religion: most Western religions victimize the suicidal. In a lot of Eastern religions, suicide was/is honorable.

2) It is about a perceived loss of control over ones circumstances. Depression operates the same way, and through ignorance, some people believe you can just will yourself to be better.

3) Fear of the unknown: "There's a chance you could have had w good life if you overcame this obstacle." Many see suicide as a permanent solution to a temporary problem, and often they are right. Often they are wrong. So there's a survivorship bias there.

4) Projection: "Okay for me but not for thee." It's hard to understand the issue without dealing with it first hand.