First we shouldn't be surprised as these courses are primarily operated by the PGA Tour. Thus they don't have to share any revenue from the course owners, as they typically have to do for other tour stops. I just looked this PGA tour year's schedule and they are playing on:
Shriners Hospitals for Children Open
TPC Summerlin Golf Course, Las Vegas, NV
Waste Management Phoenix Open
TPC Scottsdale Golf Course, Scottsdale, AZ
Valero Texas Open
TPC San Antonio, San Antonio, TX
Zurich Classic of New Orleans
TPC Louisiana, Avondale, LA
THE PLAYERS Championship
TPC Sawgrass, Ponte Vedra Beach, FL
FedEx St. Jude Classic
TPC Southwind, Memphis, TN
Travelers Championship
TPC River Highlands, Cromwell, CT
The National
TPC Potomac at Avenel Farm, Potomac, MD
The Greenbrier Classic
The Old White TPC at The Greenbrier, White Sulphur Springs, WV
John Deere Classic
TPC Deere Run, Silvis, IL
Dell Technologies Championship
TPC of Boston, Norton, MA
There are 49 events (counting opposite field events) and 11 are at TPC courses. Now I'm very happy that all PGA Tour events are set up as non profits and give away a substantial amount to charity. However, in cases where the TPC's are used does this increase the charitable giving because their expenses are less for they are utilizing their own courses? Does the PGA Tour collect their xyz fee for hosting an event as the course operators? Not sure.
In any case I don't particularly enjoy the TPC courses, especially the greens IMO. So to have 1 out of every 5 be TPC's I think is a bit much. Thoughts?
BTW referencing the TPC list they have 14 public courses and 17 private courses. Harding Park is a TPC now?