Not always done in a patronising way, but women who imply that women who make an effort with their appearance (wear makeup, dresses, high heels, etc) must have deep rooted insecurities.
It's almost always done in a patronising way when coupled with words to the effect of 'I couldn't possibly have time for something so superficial!' when in reality it takes just as long to put heels on as it does other footwear, less time to put on a dress than a tshirt and jeans, and for those of us who have worn makeup since our late teens, less than 10 mins to do a full face.