The mailsack is about peeks, teases and perception. Just like nearly every woman knows when she's showing some cleavage, or her skirt is short, or a button is undone... the moment that some clod says "oh baby, show me more. You know what I wanna see!" the game then ends, she acts/gets embarassed and there's nothing for anyone to see until she wants to play the game again. Attempting the "this has gotten boring" ploy doesn't work with them either. They know that we're waiting for a glimpse of satin, cotton, or silk and will be here waiting until they "oooooops, I hope no one saw that! tee hee heee".... yeah. That's the game, and it's voluntary to play.