I think there are numerous reasons for this. There are the obvious ones:
We are TOLD to think life is precious- by religion, by society- for possibly nefarious reasons- to ensure that we survive and pay our taxes.
We are (hopefully) TOLD we are precious by our parents because they (hopefully) love us. Yes- it could be argued this is simply a biological trick to ensure that those genes survive. Still- some people feel love to be an important part of their lives. Feelings may have a biological purpose but they are also things we FEEL. We are both emotional and thinking creatures. It may well be that some believe they are at a more evolved level where they can out-think their emotions but lots of humans can't. Their feelings of connection to other human beings are why they (should) respect the lives of others and may well grieve when those people die. (Of course in practice- this doesn't always work.)
Our ego I imagine is a strong element. We are perfectly capable of convincing ourselves that what we are achieving is all important. That even our souls are important because they are immortal. We are also perfectly capable of convincing ourselves that we are utterly useless. That all life is utterly meaningless and cruel. Our brains CAN do both. Which is right?
I'd agree with you- that there is an incredible amount of suffering in this world. There doesn't seem to be a reason for it either. So- is there a God or isn't there? Guessing you're answer is 'no'. Then- who or what is torturing us? Life? Does life have an end goal? Is life conscious? Is it capable of acting malliciously? Maybe it's chance. Is chance good or bad- maybe it's neither- maybe it just IS. So- does that make life intrinsically good or intrinsically bad? Perhaps neither too- perhaps it just IS...
Of course- where I would agree with you is- bringing a life into this world is (in my opinion) unfair because (in my opinion), the bad outweighs the good. There's EVERY chance that that person may end up struggling and depressed. Still- unless you know otherwise- life doesn't come about by magic. It is born from creatures too randy or in love to resist having sex.
There are so many questions you raise in your post which I could write a book on each to provide my proof for. But let me just disprove that there is a God and then no afterlife. Anyone who wants to believe in God or religion don't read this because these are just my beliefs .
This is just one or a few reasons why I don't believe there is a God or afterlife but i have thousands based on research I did on the brain books, the cell , evolution , Dna, ai , neurosience , biology etc.
One of my understandings of some religions is that there is a God or programmer that is watching you. Ok so how boring would it be for a God to watch me a monkey all day long . I would go absolutely insane with boredom watching me any human or a monkey mouse all day long. What do I do all day the same crap every day I have to to exist in this hell , sleep get up , shower , dress, wash clothes , clean , take out trash , wash dishes , eat, brush teeth , grocery shop work , fix problems , work all day long and many other same ridiculous crap. I hate doing all this crap every day that are boring to me much less to someone else a god or programmer to watch. I say programmer to debunk the computer simulation argument too. And to further say that this poor being has to watch all 8 billion humans at the same time. Ok a human has 50,000 thoughts per day so all those are monitored and judged too by God ? This sounds so implausible and for what reason to create animals that will suffer , get diseases , accident and suffer extreme pain and agony for years sometimes and then die. Why is that good or good to a supreme being to watch humans / animals all day long?
Why would an omnipotent superintelligent being sentence itself to watching 8 billion humans doing the same boring things every day? I don't see a reason.
I don't know maybe it's me but i don't see the purpose in a bug, rat , or me crossing the street eating , being hungry suffering , getting diseases, becoming old and dying anyway. I think i am the same as that fly , rat or monkey .I have 92% the exact same genes as a rat , I don't see why that considered so good for an ominpotent super intelligent being to create and then observe .
What makes sense to me is that Humans wrote books saying God is watching you so you have to do A, b, c or you'll go to hell . And that is to have power , control , influence over other humans.
So there is no intelligent design to life not created by a God. Life was just an accident of chaos. Random chemicals combined for millions of years of chemical evolution to finally result in a DNA molecule that could replicate itself around 3.7 billion years ago. DNA is a consequence of chemical reactions and doesn't know you exist but it's only purpose is to replicate
DNA, the hereditary material, may have appeared on Earth earlier than has been assumed hitherto. Ludwig-Maximilians-Universitaet (LMU) in Munich chemists led by Oliver Trapp show that a simple reaction pathway could have given rise to DNA subunits on the early Earth.
www.eurekalert.org