Hell, some day all women will end up with saggy boobs. It's the nature of having them. Men ought to be more grateful for being allowed to see them and fondle them regardless of sag or not.
And, guys? Some days your balls will be saggy as hell, too. Seriously, I used to working as a nurse's assistant. Old guys would have their balls trailing into the toilet when they sat there.
Oh, I think that's entirely different. If you have to have a mastectomy, hell yeah, get some implants but, if not? Seriously big tiddies (are y'all happy?) are not all they are cracked up to be. They get in your way, they make your back hurt, they make you have to pay hella more for bras.