The WHY-question obviously is a very fundamental question concerning CDing. We spend a lot of time to find an answer.
But the answer "Because it is a part of your personality" seems not to be very satisfying and the search goes on.
Instead pseudo-scientific gender tests, roumors that it could be due to a close relation to the mother, weakly significant statistics being the xth male child, hypotheses about some hormone splash in the womb etc., digit ratios with a very broad overlap for the genders, and the like seem to be more "believable", though non is even close to be proven.
What would be the difference or consequence if you would know for sure why you crossdress, and why is "part of your personality" not enough?
What would change ?