Because suicide is directly bringing to question the meaning and value of their lives and what they hold dear, like money, status, society, how could someone want to die when there's so many things to be enjoyed. Life and living better than someone else needs to have fundamental value or society will collapse.
Also because those that have not experienced extreme emotional pain just don't understand how it could override someone's desire to live. It's difficult to empathise with, this one I understand, as I'm sure most here were not suicidal at some point in their lives and perhaps found it difficult to understand at that time.
Also people take it personally, how dare you not want to live I've given you everything. Some people just don't know empathy.
Also I guess everyone's feelings and sanity is fragile, they don't want to be brought down, think negative thoughts about their own lives, suicide is by definition not life affirming, kills their positivity, which many needs to protect their own sanity, so they stay away, refuse to think about it, let it be someone else's problem
Also it's just not a popular opinion and people don't want to be perceived as bad people, or perhaps maybe they are themselves suicidal, peer pressure
I like to think when someone ctb the first reaction most people should have should be wow, they must have suffered, society really let them down, how come people around them didn't know, everything society is doing must be not working because numbers are not decreasing even though it is much harder to ctb. Let's not let it be another statistic and do some different thinking about this issue. Let's not let our own fears of social collapse and exhistencislism get in the way of actually really helping people in need, something needs to happen that is different, let's actually ask the people that want to ctb and actually listen to what they say for a change