You assume that man needs a purpose. That's just placing your own bias, wants, demands, needs, hopes, desires, dreams, etc on existence. There is nothing in the universe that suggests man is here for a purpose (except the Bible). Perhaps its that longing for purpose that drives people to religion as much as a childhood fear of burning in hell.
We know that robots are designed by humans. We have no evidence to suggest that humans were designed by any particular intelligence, supernatural or otherwise.
Personally, I think humans were designed to be Pirates by the Flying Spaghetti Monster. Yarr.