"Each round all participating players must get an opportunity for the button, and meet the total amount of the blind obligations. Either of the following methods of button and blind placement may be designated to do this:
Poker tradition has a lot to do with the fact that both of these methods are in widespread use, but neither method is superior in all situations. The moving button makes sure no player gets the advantage of last action twice on a round (a big advantage at no-limit or pot-limit play). On the other hand, a player may get to post a blind when on the button, which is more advantageous than posting in front of the button. The moving button creates a situation where two big blinds may be posted on a deal, which speeds up the action. At tournament play this speed-up can be undesirable, as when dealing is being done hand-for-hand to balance the pace of play between two remaining tables. A cardroom may either decide for the sake of simplicity to use only one method, or decide to tailor the method to the game and situation.