13 out of 16, and depending on who you ask, all 16, of IndyCar's races will inevitably feature harder racing and more intensity than any race you will find NASCAR or IMSA run. The problem isn't what you think it is.
The villain? The length of the races.
One of the greatest challenges in racing was having a car that was fast enough to win and reliable enough to finish. To finish first, you had to first finish. In his career, Junior Johnson suffered 132 mechanical failure DNFs and 33 crash DNFs in 313 races. In his career, Jeff Gordon only had 99 DNFs total, with 37 mechanical failure DNFs and 62 crash DNFs in 806 races. For Gordon, he had 9 handling (most of which were due to accident damage), 2 fuel pumps, and 1 ignition. The rest of his mechanical problems were engine. Johnson broke 3 a frames, 4 axles, 2 ball joints, 1 battery cable, 5 bearings, 1 brake cylinder, 1 set of brakes, 1 bumper, 1 carburetor, 6 clutches, 1 coil, 1 control arm, 2 differentials, 2 distributors, 1 fan belt, 1 fuel line, 2 fuel pumps, 2 gas tanks, 2 ignitions, 1 king pin (probably lost), 1 oil leak, 1 oil pan, 6 pistons, and 1 multiple piston-failure. He also was disqualified twice, suffered fatigue once, and quit once due to accident damage. He suffered 14 overheating issues, and blew 28 engines.
Granted, Junior was the king of breaking stuff, but Mr. "Wait and strike" himself David Pearson had 204 DNFs in his career, of which 41 were crash, 1 was a non-start, 2 were disqualifications, 1 because he quit. The car itself broke 159 times in his 574 starts. Extrapolating, he would have 286 (rounding down) mechanical DNFs if he ran 806 races, or almost 8 times as many as Jeff Gordon.
Last weekend, the Rolex 24 was a debacle due to a BOP change that wasn't publicized until *the middle of the race.* And fans got to watch 41 out of 54 cars finish a 24 hour race, with 17 cars across 3 class within 25 laps of the overall winner. In 2007, 25 laps down would have gotten you 8th overall. In 1998, it would have gotten you 3rd overall as the actual 3rd overall car, a Porsche 911 GT1, was 44 laps behind the winner, and 33 cars finishing, albeit most 100-516 laps off the pace! Danny Ongais, Hurley Haywood, and Ted Field drove the #0 Interscope racing Porsche 935/79 to victory in 1979 by 49 laps over the Ferrari 365 GTB/4 of John Morton and Tony Adamowicz, with 9th overall 105 laps down and 14 cars finishing.
Mechanical reliability has rendered the endurance of racing meaningless. 24 hour races are now worthless, never mind 500 mile races. As such, having such races in these series really is pointless. The only difference is that you need 3 drivers to run a 24 hour race effectively, but Louis Rosier drove all but 2 laps in winning Le Mans in 1950.
This is why there is no effort seen in NASCAR races. The cars will finish, so they might as well wait for the late debris yellow and charging late. This is why NASCAR is giving points at the 1/4 and 1/2 points: to encourage racing prior to that late debris yellow.
I think NASCAR would be better served by the unused proposal. Split the field for 2 25-50 mile heat races that pay points and then run a 150-200 mile feature that pays even more points. This system could be used across all three touring series. Each series could be a 1 day show, with a 60 minute practice, 15 minute qualifying, heats, and then the race. Run clean, fans could arrive at 10 or 11 AM and be out around 4 PM. Trucks on Friday night/Saturday early afternoon, NXS Saturday morning/Saturday late afternoon, and Cup Sunday.
And with the rate both series are losing vehicles, maybe we'll see Cup and Trucks running combo races soon.
Edit: note that this could also be applied to sports car racing. Why run any races longer than 2 hours?