Why? That is a great question that has been bothering mankind for millennia. See, the more you dig into it the more it becomes apparent that life has no meaning. Maybe it is never supposed to have any meaning. Looking for a meaning is the thing that takes you away from what life is. The body you have is unapparelled in nature. It is like a finger print. Not two are the same. It is an extraordinarily intelligent organism and it never asks the question "why".
It is your thought that wants to analyze and figure out what life is. What is a thought? Where do our thoughts come from? Surprisingly if you look deeper, you will realize that everything you think you are is a thought. Your past experiences, conditioning etc etc. Thought likes to hold on to the past and always projects the future based on it. It wants eternal happiness without one moment on unhappiness. It is a protective mechanism which wants all, and if it doesn't get what it wants then it wants destruction. Even if it gets what it wants, it wants that to last forever. It wants permanence. But surprise surprise, there is no such thing as permanence in nature. The only thing permanent is the life energy (which we will get to in a bit)
This same thought functions exactly the same way from micro (singular, you) to Macro (world wide)
Here's where this game of life becomes a cosmic joke. The actual reality is, the thoughts that dictate your life and consume tremendous amount of your energy is actually not you. What you are is just pure life energy. Like an animal out there, which never asks the question what the meaning of life is. It just functions from moment to moment. It does not care or think about what society thinks or does for it. The human organism has almost no needs. The only things it needs is shelter and food. Even food doesn't have to be fancy. And reproduction, not as a means of pleasure but as a means to reproduce itself just like any other living organism.
The entire universe and all its contents are one unitary movement. You are not separate from things around you. I am not saying some romantic stuff. It is the fact. Its your thought that gives you an illusion of separation. Why do you think people look at astronomy to predict ones future? It is because the planetary movements and all living organisms are one unitary movement. These bodies are hijacked by this knowledge, conditioning and bundle of memories which all center around a "self Image" and that's all that is, an image. Not real.
So the reason all religions are against suicide is because, when you are taking your life, it is your thought/ "fear" a dead thing taking away something living. How this illusion of separation happened which is also known as "Self consciousness" is anybody's guess.
Truly, really nature does not see any distinction between you or the people responsible for your misery. It is one singular unit. Your thoughts are "materials" non living, the bodies have a natural clock and when the clock runs out, they breakdown in their constitutional elements and continue to feed other forms of life in the soil. For nature there is no such thing as death!
The question is then what really are you? The real you is that true intelligence that beats your heart without you thinking, makes this body work like clockwork. It is the pure energy of life. And that energy has no beginning nor end.
Understand this, don't take my word. Go out research it, then it will hit you that how extremely silly all our life's so called problems are. They mean nothing. Because they are nothing.
Once you get this, then you will not try to live life, neither will you try to be happy. Your psychological fear will fade away. You will function harmoniously with the things around you, not with any agenda, but because you know the truth. Once this happens life takes place. Once you let go off all desires and function harmoniously with the people around you, you'd be surprise then how things will start falling in your lap.
Let go of trying to live life or understand life. The one that is asking all these questions is the thing that's taking us away from it. Wish you best!