I know it's just eye candy for horny dudes, but that doesn't change the fact that game developers purposely put in boob physics and claim it has realism because of said boob physics. Even in games that take place in Medieval times or Ancient Japan, supposing that there's female action heroes with huge knockers, surely they would have found a way to stop the jiggle?
If I were an ancient japanese action hero with double H breasts I would probably find some way to tie them down so they don't flap in my face while I'm fighting evil.