Ever here of the theory of diminishing returns?
It states that when you don't have something you are craving for once you finally get it the first time, it's an awesome feeling of fulfillment (whether it be pizza, blowjob, cocaine, driving fast, or jerking off to Playboy, etc.) It doesn't matter what the source of the buzz, that first rush is overwhelmingly exhilarating. So you do it again, and again, and again. But after awhile you become conditioned to it, your mind and body began to just achieve adequacy, not that overwhelming exhilaration you first felt. You eat 4 slices of pizza, that 5th slice isn't gonna do shit for you. You snort 10 lines of coke, that 11th one really isn't gonna do much for you (yes, I had a wee little problem many years ago).
And you can only stroke the meat bat so many times to playboy before it just starts getting old. You wanna see something happen, you want that chick to get a little adventurous.
And that's when you start looking for chicks with cum all over there face, foot long cocks up their ass AND in her mouth AND in her pussy AND one in each hand. You start looking for what you haven't seen before.
IT'S human nature.