Personally, I think it is all rubbish to speculate on why or why not the owrld must exist rather than to get back to the real question of why we exist.From a strictly logical standpoint, I cannot answer that by strictly saying that by some universal throw of the dice, conditions just happened to be right for life on earth. Its cold, rational, and un-philosophical as pertaining to humans.
I believe that God has a specific purpose for each one of us. I believe that we are special in His eyes.
Each one of us has different needs in order to complete our sense of self, our perception and acknowledgment of our destiny, and our overall drive as a species.
I don't believe in the simple and coldly emotionless "survival of the fittest" merely for survivals sake.
I believe that the purpose for why you exist and why you ask us these questions is tied in to a larger and very important plan.
We all want to know why we are here and why everything is as it is.
I have personally seen young people who never had active Fathers who were more pessimistic and clueless regarding these questions, but overall that was no definite excuse---it was more of an observation.
Sometimes, other humans can't give you the answers that you seek.
God can. (Spiritual perspective)
Science can answer a lot of questions in a fact based reality as well, but it by no mans should prevent you from being a philosopher, should you so choose.
Thats my 2 and a half cents worth!