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.
I can’t think of a sport where the local level or amateur leagues fund the professional level. Why would they? High school football doesn’t fund the NFL, beer league hockey doesn’t fund the NHL, etc…. Sure the participants may buy the product because they like the sport, but their costs to participate don’t include a direct subsidy. That’s why their tax dollars have to be used for the owners’ stadiums.
Governing bodies OTOH do fund pro events in some cases, but generally one championship. The USGA and R&A putting on the US Open and Open Championship respectively, as well as corresponding women’s and seniors opens. These events have some amateurs still, but are basically pro events now. Pro tours and governing bodies are separate in all the sports I can think of.
League pool has its own model and seems to work. Multiple leagues make a go of it. I think the UPL may use the league to promote professional pool. IIRC the website of the English business said that. I don’t know how the US UPL fits into that. We’ll see how that goes in time.
The formula for pro pool being a stable, successful spectator sport hasn’t been worked out/ stumbled upon. It would be nice if it did, maybe the WNT will work long term.