At the core of life is one purpose- to survive.
This is not what lies at the core of intelligence, which we developed to survive.
Humans are given the ability to question our core purpose through intelligence- this is, unsurprisingly, incredibly uncomfortable.
Discomfort is to be avoided. Questioning our core purpose is a failure of evolution. Ants will never consider what it means to die- they only strive to live.
In my eyes, this is what many humans strive to return to. The bliss of a singular goal. Survival, without any question to what that means. Without having to think about all the details, or anything else. A nice, orderly line to follow and a few rules that will make everything okay at the end of day.
A binary. Failure, or success. There is no in-between, there is nothing else.
It is incredibly against this, then, to think about what life means. What the value of suffering is when it's not their own. About ourselves in the scale of the universe. Anything larger or separate than the individual and what lies directly in front of their eyes.
Suicide brings many of these questions to the spotlight- if our only purpose is to survive, then why would anyone want to do the opposite of that?
To accept that it may be a reasonable decision is to accept that these questions are worth our time and thought. Most people are unprepared to do that.
Ignorance. Consciously or otherwise, that is what these people want to keep. Life is easier when you have easy answers. Even if they're wrong, and often harmful to others you can go on believing they're right so long as you keep from questioning them too much. Especially when you can avoid seeing the consequences.
Willfully ignorant, is what I like to call it. Honestly I understand the thought process, though that's not to say I agree with it at all. I feel it's incredibly selfish.
Survival is no longer at our core. We are split between that and understanding. We should find what is at the core of both, even if whatever lies there may be uncomfortable.
To do that, though, we'd have to accept that maybe survival isn't all that it's been advertised to be. Maybe that core, too, is not inherently good.
There's reasons so many people tap out- and I wouldn't call all of them "giving up". There's more to it than that. But society needs to evolve, first, which it may never do.
Tldr;
Our duty, in their eyes, is to keep their world view all warm & comfy, they don't want to see the world as messed up.
So we must be crazy to suggest otherwise.
Apologies for the rant. I hope it all makes sense.