There are so many misconceptions about health and death before we even start talking about mental health and suicide. The public needs urgent education about the facts of life and death as the lack of knowledge is startling. (A friend's currently devastated as her pet has developed cancer. As I was trying to comfort her, she shocked me by saying that she didn't know that animals could get cancer.)
People aren't stupid but they're acting in ignorance and when it comes to things like suicide, well meaning attempts to help can often make things worse - and nobody likes being told that they're in the wrong, especially after years of believing something.
Ironically, I must confess that I didn't know much until I started to face up to my own mental health, self harm and suicidal feelings. Hell, it's been years but until this year I didn't know about active vs passive suicidal ideation!