It's a tournament with only 1 pooltable, with a big crowd and all matches being televised.
A race to 20 would make the tournament 2,5 times longer, less of the matches televised and half the audience.
Race to 8 & alternate breaks makes it exciting for tv and audience. Long races are great in gambling, but not on tv.
It is a real tough field... You've got all the top European players like Ortmann, Engert, Souquet, Feijen, Petroni, van den Berg, Tony Drago, Imran Majid, the Chinese who finished 3rd in the last WC, the 2 last double-world Champions Wu and Alcano ++ (I certainly miss Strickland or Schmidt in it)