Suicide is a symptom of some types of mental illness. But perfectly sane people can still kill themselves. If one wants to prevent suicide one has to accept that fact. We cannot prevent suicides if we look only to people with some sort of observable mental illness. Normal everyday people, some in the prime of life, can and do occasionally decide to kill themselves.
Aside from extremist views (ie never/always appropriate) our society does generally accept suicide in some circumstances. We give medals to people who knowingly die in order to save others. Our movies are full of characters deliberately killing themselves for the benefit of others. On rare occasions we openly criticize those who do not kill themselves where we expect them so to do (Gary Powers). It is part of our culture. We can debate whether suicide is an appropriate action in various hypothetical circumstances, but that's a rambling debate with no end.
Imho suicide is a private issue. In most circumstances our society should work to prevent it from happening, but I'm not going willing to describe every suicide as the result of criminality or mental illness.
