i would partially align it to religion and a "higher power". i think that it's a combo of lack of religion, too much knowledge and not enough wisdom, as well as lack of fulfillment.
i'm using those as a bit of a blanket to cover a very varying circumstance. these topics are intensely deep in itself, i'll acknowledge now that a lot of this will be opinionated and debatable. some of it will be relatable, but perhaps only to me.
in various form, religion usually offers life after death. it is the greatest reward you could receive after losing your own. people have died in peace and in war, but if they share a religion, they all have expectations of the same reward. it's nearly impossible to imagine that this reward may not exist if you are expecting it. it is literally blinding and will control your life, especially when there is also a punishment that you should expect if you step outside your boundaries. (good or bad it happens)
...when you don't expect either reward or punishment, you are no longer bound by the chains of faith.(again, good or bad) at this point, all you can do is expect "nothing". less than nothing, an absence of self. you can put hope against the odds that "something" could happen. "anything"... but if you don't believe in religion, you probably don't have high hopes for anything specific.
i think it's fair to say people are somewhat generally aware of the suffering of death. most everyone says they want to live and die old but... do they actually want to die? or do they just want to be old and magically transcend passed the reaper without suffering? it's easy to ignore, but any one of us could suffer torturous medical conditions for years before we finally "stop suffering". without a binding chain such as religion or fulfillment in life, it almost makes sense to make it easier at times. without "reason", it would be much easier to commit to suicide at sign of extreme medical conditions, or when running out of money to address them effectively. it would even be easier to commit at whim if negative emotions engulfed the positive.
i will add to this, i've been wanting to make a topic kind of similar to this. i think i'll do better at this not trying to rush thoughts into 1 post.