Does racing sell boats? Maybe to the hardcore go-fast guy with lots of money, or to a guy that wants to go racing. However, I'm guessing that for the vast majority of performance boat owners, there are about 101 other criteria that come before "racing performance" on the decision checklist.
IMHO, powerboat racing today just doesn't have the return on investment that most boat companies look for when making these types of commitments. The proverbial average boat owner is more likely to see himself and the Mrs entering a Poker Run than he is strapping on a helmet and hitting Key West. And there are a lot of boats that make good poker runners that will never see a race course.
Take me, for example - middle class guy with a good job, married, one kid, more to come. When we go boat shopping, I want a boat that is quality built, runs decently fast, good factory support, etc. The Mrs wants a nice head, room to stow all the niks and naks that come along, safe for the young'n, nice amenities. We both want a boat that fits how we use it. It might be great that a Cig or Donzi or whatever can run WFO around a course for an hour or two - I can say with authority that I will do that exactly zero times. What I want is a boat that can run through the local lake slop at a comfortable cruise, with high freeboard and a secure ride, with a pottie for the Mrs and a nice cabin for the kid. If the factory races, great, I get bragging rights at the bar. Otherwise, it's a non-issue.
Add in the cost for a factory to go racing, both in time, money, and resources (not to mention the politics of APBA vs SBI), and I think the cost/benefit just isn't there.
As always, YMMV