Why? When I am dressed and look in the mirror, I see my real self. The male is less recognizable. That of course begs the question, of why yet again, and that gets into some very murky and unresolved questions about genetics/epigenetic, birth order, social influences etc.
My guess is that your wife is not asking for a list of possible biological or sociological contributing factors. My guess is she is asking your personal reasons for choosing to cross dress. Any answer you give will be legitimate and at the same time probably unsatisfactory. Your answers were that you felt, enjoyment, excitement, younger, fulfillment (feeling whole). I suppose the follow up question is, but why do you feel any of those things, which as others have pointed out, it like asking a person why they like Limburger cheese or running a marathon (I know, its crazy, but some people actually enjoy running!)
Perhaps the key is in that term, “fulfillment”. As you said, dressing and going out as a woman makes you feel whole. That suggests/implies that it fills something that is otherwise not satisfied by male gender identity, that a part of your identity is female and needs expression (lets skip over causal factors entirely).
Humans like easy, either/or answers. But we aren’t that simple.
