While competition is a driving force, and a title is certainly attractive, I believe this huge amount of money is the driving force for this competition. Winning is important. Individuals who compete in this field are obviously driven by their desire to win, but underneath the competition is the strong desire to win a large amount of money.
Too often, we cynical post-modern consumers and citizens of the world are willing to write off someone's efforts as having been "just for the money". This phrase could be used in reference to anyone from an entrepreneur, to an artist or musician, to a professional athlete. But I think this mindset is far too simple and doesn't even come close to comprehending the complex relationship between financial gain and the public prestige that come with any kind of celebrityhood. Ultimately, both are gratifying.
Yes, the World Series of Poker is about the money. If the World Series of Poker was played with no prize purse, there would be much less players involved and certainly not the high end players. You can see this proof just by looking at some of the smaller poker championships that do not get a large turnout.
Poker is great. Sometimes you are good enough to take home a little money, but sometimes you are not good enough and leave home empty handed. But the whole purpose of the game is to beat the player on the other side of you. Period. It is a mind game, not a money game.