IMHO:
* You don't need to be big/ripped to have taken the juice. Look around the board! 95% of the board members are smaller than Dre, Carrot, Bale, etc. I'd give maybe 30-40% of the board members Edward Norton's size. Many of those people are taking various forms of anabolic steroids.
* The celebs have the time, the money, and the motivation (the "role", the "look", etc), so why wouldn't they? Just because they don't look like professional BBers or WWE wrestlers doesn't mean they don't juice. I'd guess a large number of the people in that list did/do take various pharmaceuticals (including AAS) because they CAN.