Villains are so busy with being all-powerful and trying to conquer the world that they so often completely neglect their physical appearance. I mean, take a look at old he-who-must-not-be-named here. Long fingernails (and a not very healthy-looking purple color too), weird veins, unnaturally-colored hand skin...come on, man. You're all-powerful. The least you could do is cast a spell to give yourself some better looks. Oh well. As long as he's obsessed with ridding the world of Muggles, he just probably doesn't care that much about anything else.
