Attendance at NASCAR races is down across the country, as are television ratings.

While the sport and its tracks are on solid financial ground — courtesy of a 10-year, $8.2 billion TV package with Fox and NBC that runs through 2024 — no one is sanguine about the apparent shrinking interest in the sport.

Sunday’s Crown Royal Combat Wounded Coalition 400 at The Brickyard  at Indianapolis Motor Speedway was the latest sign of decline, registering the lowest estimated attendance in the event’s 23 years — about 50,000 fans in stands that can accommodate 250,000.

Mark Miles, CEO of Hulman & Co., which owns the Speedway, said the Brickyard 400 is important to the company and efforts would be made to rebuild audiences.

“It’s a big place,” Miles said. “When you use the whole stands, it takes a really big crowd. It’s an event that’s important to us. I think it’s important to NASCAR and to the NASCAR paddock, so we are just going to redouble the effort to grow it.”

Miles said that Sunday’s high temperature was a factor in crowd size, but that more could be done to boost attendance. “We are going to keep working harder and really up our game so, really, we can do justice to May here  … and focus more energy and resources on the Brickyard as well. We will build from here.”

Beyond Indy, the International Speedway Corp. and Speedway Motorsports Inc. — the publicly owned corporations that operate 20 of the Cup series’ 23 tracks — have seen attendance revenue fall. According to a review of the companies’ annual reports, ISC’s attendance revenue is down 49 percent from its highest point, in 2007; SMI’s is down 46 percent from its peak, in 2008.

Why is NASCAR struggling? Five  theories:

The U.S. recession that started in 2008 hurt a lot of NASCAR fans. In addition to wiping out 8.7 million jobs through February 2010, it caused gas prices to spike above $4 a gallon — prohibitive for fans who had been making road trips to see races. When USA Today asked 200 fans at tracks, on the phone and on social media to explain why they’re attending fewer NASCAR races, one of the biggest factors they cited was the cost of travel — hotel rooms and transportation.

Changing times: Established stars are hitting retirement age. Jeff Gordon, 44, officially retired last year (though he raced Sunday); Tony Stewart, 45, has said this is his final year of full-time racing. Dale Earnhardt Jr. is 41 and Matt Kenseth 44.

Changing times 2: Technology lets younger fans keep up without buying a seat. “The struggle with keeping fans engaged as the Baby Boomer generation is exiting and the younger millennial generation is entering — the struggle is real,” 2012 Sprint Cup champion Brad Keselowski said recently. “You see that with the technology we have today: It is easier than ever to get access to different platforms without attending.”

Changing rules: Another top reason USA Today found in its survey was discontent with NASCAR’s competition-related decisions and constant rules changes. A big one: NASCAR changed its playoff system in January 2014 to create a winner-take-all race among four drivers in the season finale, as opposed to rewarding consistently good performance (but not necessarily victories) throughout the season.  “The constant changes NASCAR does, it doesn’t have the same good feeling it used to have,” Lanette Williams, 63, told USA TODAY Sports. “We’ve just lost interest in NASCAR. NASCAR has lost interest in us.” She and husband Jim chose to travel and see more of the country instead of spending many weeks a year following NASCAR.

Different experience: Instead of a midway with souvenir haulers, there’s now one merchandise tent area. Pre-race entertainment such as the Sprint Experience and Fox’s “NASCAR RaceDay” TV stage are gone.

Forbes contributed to this story.