I'm not so sure your ideas are relative to the true subject of the decline of golf. All of my contacts within the PGA, PGAtour indicate that they are extremely healthy in sponsorships and revenue gain year after year. These corporate sponsorships are fueling fundraising and their own product, service and consulting services on tv and publications. Basically marketing dollars. There has not been so much as any downturn at all including when tiger was not playing. Almost all these companies that advertise and by tents etc are going after People with money and unfortunately your 20,and 30 something do not have money. Ever see a 25 year drooling over a Cadillac, or shop for insurance and investment brokers for example?
Now to your point smaller businesses can no longer write off golf as an entertaining expense,so that scramble tournament in any town USA will have trouble getting the local restaurant, construction company, local insurance, doctors offices will likely no longer be contributing and playing in that $400-$600 foursome. Thus tournaments including member/ guests may not be a full field.
I was speaking to local golf as this is more of an indication of the downturn in the game of golf...not sponsorships on the PGA tour or revenue. The health of the PGA tour doesn't reflect on the local country clubs or municipal courses.