Actually I think APA is sitting in the Cat Birds seat. It has the largest membership of all the pool organizations active. For some reason they keep their amateur status and don't raise the prize pool?? They hold at least two LV stops yearly for about 10 days with 7K players attending for a very mediocre prize pool. I think they could pass all the other organizations in a couple of years if they really wanted to. They seem content where they are at.
The APA is a business. They cater to players who average an APA 4-5 skill level. They do sponsor top players for events, such as exhibitions. I think Earl did some and Jeanette Lee and Fedor certainly have. But their main goal is to make a profit and evidently they don't see a way to do that with pro events.
I don't think it's the prize money that brings the APA players to Las Vegas. I think there are over 10k players now at the APA national events and the CSI combined events in March bring in about 13,000 bodies. On average, it's a moderately expensive vacation.
I think it would be great if US league pool did support a pro tour, but beyond CSI hosting the PBS events in March, I don't see it happening. If each league player in the US paid $5 per year towards a pro tour, that would be over $3 million. If a million came out for production costs of a tour, that still leaves two million for added money. It's not going to happen because that money would effectively be coming out of the pockets of the league businesses.