I have a feeling that people underdress because they are closeted. Because they are unable to give an outlet for their CD side. This is my assumption based on experiences of myself, pre-op TS on hormones and some other cd'ers i know who go out.
Correct me if i am wrong.
EDIT: Use your own defn of closet. I am just interested to know about underdressing and its relation to being in closet.