Name value puts bums in seats.
WWE make the point RAW is THE brand, it has the biggest draws on in Triple H and John Cena, its live, it gets the attention, heck even on this board we talk about it more than the other brands.
Ratings here in the UK from the other week had, Smackdown 87,000 and Impact and RAW in the 35-40,000 range from what I remember, although obviously RAW being live then repeated splits the fans, still thats pretty damn good for Smackdown.
A lot though ultimately is the stigma of it being the #2 brand. You take the roster, swtich them, and I RAW would probably still win in the ratings.
This is for the US fans to inform us, but I do believe I read RAW is available to more viewers because of the network it is on. Also Friday nights is soon as the worst slot for television programs.