Al Schroeder (alschroeder) says: Same reason she fought Lafferty in the beginning of the storyline taking the costume off. A) she's fur covered in that form so it's not like she's streaking---it's like wearing a furry leotard-- and B) she can move around a lot better without it.  Plus, if she switches to the falcon-form, it would DEFINITELY tear. It's easier to operate that way for her, and gives her more options.