Because there may be 100 things before it, so it's only 1% of what lead up to the event. & the things which came earlier had a longer time to cause impact. ie a series of early events can lead to a result, whereas what is the actual percentage of people immediately committing suicide after listening to something suicidal? Better to focus on how to mitigate people reaching this point, as opposed to the straw that broke the camel's back