Major championships in any game or sport are ultimately to determine the "best of the best." The real-life U.S. Open allows everyone an opportunity to qualify but it is the rare lower level player who will qualify and even rarer that one will make the tournament. Rarer still is one of those qualifiers who makes the cut, even rarer that he might be competing for the win. That is exactly the way it works here as well.
If you want to make the argument that WGT should have other championships based on tier (World Amateur Championship, World Pro Level Championship, etc.) then I think it's a good suggestion to consider. John is right in his observation, though, that higher skill level players who create multiple accounts will dominate those tourneys.