This thread may never have an end to it, because there is no solution. I am perfectly happy to accept that we are just here, and have to make the best of it while we are. It hasn't stopped me wondering 'why?' in the past, it's simply the conclusion I reached.
People have been accused of lack of imagination for not asking 'why?', even for lack of intelligence. I think some are simply more accepting and chilled about it. I don't believe there was a specific purpose behind our evolution, we are merely an accident of nature.