I've never really taken issue with Cortana's appearance even though I'm sure half the reasoning why she looks the way she does is because of horny artists. I dunno. I really like that reasoning Frankie gave that Cortana's appearance demands attention and thus allows her to control the situation. Not only is that kinda empowering but it's making the best out of the actuality behind her design.
Also, you have to wonder why an AI hologram would feel need to wear clothes in the first place. Screw your lame human concepts of decency.