Protecting Your Hand

I just had a poker epiphany, please give me feedback.
Here goes:
WE'll say that you have 99 on a flop of 9h8h2c. Often, many players bet out here, to "protect their hand" from a straight or flush draw. Maybe I'm an idiot, but doesen't that mean you hope you're NOT going to get called with the NUTS?!! I mean, if you're "protecting your hand," it's the exact same thing as betting out with 27o: you're hoping to win it right there, aren't you. If your hand protection works, he folds his draw (if that's what you put him on). This is the exact same thing as a bluff, nonwithstanding the possibilitiy that your opponent has A-9, an overpair or a lower set. But if you no he has a draw and protect your hand, it doesn't matter what your hand is since you don't want to get called. So then bluffing is the same as hand protection.

Could someone clear this up for me?