To a nearly-forty-year-old, they look like children, which they barely aren't, after all.
I think women don't get really hit their stride aesthetically till around thirty or so.
I'd like to see pictures of them a decade from now when life hangs on their shoulders a little more heavily and they've had a chance to acquire a bit of character.
Caroline Kennedy was kind of a ho-hum teenager, and she grew into a rather striking young woman. Chelsea Clinton's one of those gawky adolescent girls who's also improving with age. And the Nixon girls...whew....