They cant guarantee them because there are so many things that can happen. Sony gives each store an allotment of consoles. The store takes that many pre orders. Now its up to Sony to actually ship that many consoles to the store. If they dont then everyone isnt getting their console. Plus other things can happen like consoles getting damaged during shipping to the stores, employee theft, the building burning down. They dont guarantee it because things can happen. Besides something unexpected happening everyone who pre ordered should receive their console.