I don't know, it's hard to explain, I guess the best thing I can think of is: I think they're cute, you don't always see them so when you do it's kinda sexy, when girls wiggle their toes...
Umm... a good foot as opposed to a bad one? Usually they have had a pedicure, or atleast their nails are trimmed, tan feet (no sock tan lines), no crooked toes or when the toe next to the big one is longer than the big toe...