What sort of leading question is that?  The question assumes there is a purpose.  Is there?
The answer could be whatever you want it to be.

But science can't categorically say that there is - or isn't - a purpose.  It can't answer the question.  Since many people believe that there is a purpose to why they are here - after all, a lot of mental health seems to come down to 'purpose', not to mention a host of organisations and their 'mission statements' implying that purpose is a innate element of humanity, I would disagree that it is a leading question: rather, its one asked by thousands upon thousands of people every day.