What you're saying is, they all had undiagnosed mental issues, that could've been treated. And the main reason for them not getting the treatment they needed is that people with opinions like yours set the tone.
If it's really a life choice someone is considering then I'm 1,000% behind them seeking help. If they've already started dumping bodies in ravines, not so much.
One of the most popular types of medicines in the usa to prescribe to people with psychotic tendencies entirely eradicates any psychotic outbreaks, but also completely suspends the physical production of dopamine, meaning people become physically unable to feel happiness, or much of anything. They become inert breathing husks.
And since a lot of people are either of the opinion "fix yourself, or we'll fix you with guns", and the "fix yourself" step is pretty much suicide, just of another kind, it is not only normal that people don't seek help, but it would be almost crazier to actually go and seek help.
Until the USA as a country actually start caring about these people, like the citizens they are, they will have no incentive whatsoever to trust themselves to other people, and things like those in your list will keep happening.