Have you recoginze this? In a picture I look like garbage. But when I look in mirrors I look like Mr. Sexy. And no, I don't think it's because we get use to the mirror image and then we're surprised by the pic of us. I've seen lot's of girls who look really stunning on pics but were ugly in real life and vice versa.
I am not photogenic at all, but I think I'm pretty good looking. I guess it's just how it is? There's this one girl I know though (a friend of a friend) and she looks like a model in almost every picture...like it seems effortless. In real life though, she's not very attractive and has quite a bit of weight on her.
Photography is an art and so is modeling. If you take horrible photos it's because a. your photographer is unaware of the methods used to highlight "desirable" features or b. because you yourself don't know how to flaunt your strongest attributes.
You can literally take several photos of the same person at different lengths, angles, using different exposures, and make it look like each photo is an entirely different model.
p.s. girls have a clear-cut advantage when taking photo's because long hair allows you to better frame the face.