Hyper Is the New Feminine
Girls used to be expected to be sweet, demure, passive, and scatterbrained. The first three requirements got thrown out a long time ago, but the last one is back in force. It's bolstered by anime, in which characters who could wield a mean fist/fireball/legal order defang themselves by becoming squealy and perky and bouncy and eeeeeeeeeeeee! So sure, they still have all the power, but they choose not to use it! Because they're so creative and cheerful and brimful with the limitless distractibility of youth that they can't sit still long enough to wipe their ass! What a way to have your cake and completely forget to eat it, too!
So now we have legions of teenaged girls (and grown women who want to be teenaged girls) who would gag at the idea of being modest or passive or naive, cheerfully announcing right up front that they're "hyper." Some of them even follow up this shocker with the news that their hyperness might make them flaky or annoying, so pwease forgive them. In what way is this different from the good old 50's game of playing dumb?