I know that a lot of artists (and people in general) don't like body hair very much, which to some degree is why I love it so much. I love the motion of adding it to a picture, because it's something that people have and try to ignore all the time.
And especially in the case of Harry, who in my understanding, would not be one to shave his armpits--it's not like his armpit or leg hair would just disappear upon his adorning a dress. :)