Regarding the whole taboo thing, I think this is a good assessment. On the other hand though, I think talking about suicide is so taboo because people are afraid to talk about it. I don't think it is necessarily a fear of a 'void', 'nothingness' or death. Having spoken to suicidal people, there are some inhibitions and false beliefs you have to get over before you'll actually feel comfortable talking about it.
There is the idea that talking about suicide openly might inadvertently drive that person to suicide. Not true. If that person decides to kill them selves, it will be with or without your involvement. Nothing you say can make a person kill them selves. You are in no way responsible for that person's death.
There is also the idea that you are some how responsible for 'saving' that person. Again, not true, but if you actually believe it, that belief can put a tremendous amount of stress on you and totally devastate you if that person does commit suicide. Again, you are in no way responsible for that person's death.
But yah, I don't think that alone explains why it is taboo. Being afraid to talk about it doesn't explain the fact that suicide was once consider (and still is to many people) a sin in Christianity and perhaps other religions.
As Albalida mentioned, may be it is just a form of control to protect your investments. Some people were literally treated like property in the past (still are in some cases). If you are relying on someone for some form of support/investment, it isn't going to do you well if they make off and kill them selves. That sounds incredibly cynical though. I'm sure that some people who try to scare loved ones into not killing themselves simply love them and there are no other strings attached.
Originally Posted by Albalida
Put bluntly, every individual is an investment. Parents, guardians, and government funds have gone to birthing and growing a human being. All those meals, clothes, the buildings that shelter us, education, no matter how unhealthy/ill-fitting/asbestos-padded/brainwashing, all of that comes from the effort of other people.
After all that investment, there's an underlying imperative to give something back, even if you're horribly unhappy with being a cog, or everything is a pretense, or you truly live in unbearable physical or emotional pain.