Why is this important?
Because that knowledge should help us to relax and realize that we are not the ones who are to blame for the feelings. Our behaviour (such as the desire for cross gender expression) is a symptom of a desire to become more closely acquainted with what we love and admire in the other sex. As hard as it is to explain even to ourselves, this is a basic truth.
For the vast majority of us, there is only one place to go and that end point must by necessity be self acceptance. Trying to suppress or curb will only lead to frustration and depression. I know I tried absolutely everything in order to eradicate my feelings and, despite what some militant "true" transsexuals will tell you, most of us are not born at puberty; we are in fact born well before. I can easily trace my gender feelings back to age 5 or 6.
Are some so called crossdressers born after puberty? Of course they are but their motivations and modus operandi are entirely different. It is like comparing apples and oranges.
Jack Molay over at Crossdreamers will be releasing the results of an important survey which will reflect what I am saying here. Many of you may have already taken part and, if you haven't done so already, I encourage you to participate.
The results will confirm what Harry Benjamin already knew way back in 1966; namely that gender dysohoria is a graded continuum.