There is an underlying need in the human psychosis to feel needed or important. Unlike the animals we cohabitate this planet with, we as conscious beings need a motivation to exist beyond those provided by base instinct.
Let me take a moment as an aside to address the inevitable criticism of my classifying animals as non-conscious beings. Find me an animal that actually commits suicide, outside of staged Disney nature films, and I will believe that it is possible for animals to be as self aware as humans.
In fact, this driving need to be self important, or at least necessary, is the underlying reason why most suicide exists, or rather when this is lacking in the humans that then subsequently engage in the act. Despair sets in when true perspective as to our respective place and function in the universe is realized. The easiest way to crush a child’s hopes and dreams is to make that child aware of how little in the end those dreams matter and how little hope they have of ever achieving them.
This is the crux upon which all religions exist. These spiritual mythos were specifically invented to give a grander unified dream, and thus motivating force to mankind in this otherwise harsh and meaningless reality. If my actions and life’s work in the end mean nothing in the grand scope of emotionless galactic balls of gas and fire, which even in their fantastical scope are finite and without grander meaning, then why should I embark on any of them? What point does the common man have of conducting his life beyond the satiating of his own baser desires and instincts if his entire being is for not when he dies?
This leads to a quest for immortality, an extension by action or genetic legacy which will impart some manner of grander meaning upon the mediocre occurrence that he is. Even this is attacked by the knowledge that in the future this world, the solar system, and even the universe itself will eventually cease to exist, giving a finality of futility to everything that ever was and ever will be. This particular dose of practicality is a hard one to accept even for the most pragmatic, much less the rest of humanity. Thus it is, when such contemplations overwhelm many, they adopt a nihilistic rather than humanistic viewpoint and rightly deduce that if nothing ever matters then their own selfish death will be one more thing that does not really matter at all.
Personally, I would rather embark on a quixotic quest for actual immortality, or the closest I can achieve, in my own person than abandon this innately interesting life. While I may not succeed in staving off death indefinitely, I will nonetheless attempt just that until I am dragged kicking and screaming into oblivion, or whatever the unknown that is death actually holds.