In the documentary The Nature Of Existence, one of the things that stood out to me was just how poor some of the answers people gave were. For example, a Christian wrestler gave the purpose of existence to be recognising Jesus as our Lord an savior - which I guess for him is luck he was born into a society (and probably a family) that just happened to hold that as true.
Now I don't take that person as a bastion of Christian dogma. What I do wonder, however, is where someone goes from there. By accepting Jesus they've not only found the purpose of existence but fulfilled it - many of them doing so as children. Could trivial answers like this be the motivation behind belief in the rapture? Is it the underlying motivation behind proselytism - as what else is there to do?
A belief taken as a child or a young adult has to on average last some 70 years, through coupling and raising a family, through trials and tribulations that the world brings, through the good times and bad, and in the end dying. How much of that purpose is related to any of that? Perhaps one could make the argument that it does so in a secondary sense, as it allows for things such as community and a means to get through hardships. But if that's meant to be the purpose-driven life, as Rick Warren puts it, then it hardly seems a purpose worth having.