Because, for the most part, we aren't doing damned thing about it. "Rolling coal" is inherently a very public act of law breaking, but I doubt a single person has ever been pulled over by any American cop for it. The EPA and certain states were trying through other enforcement mechanisms to fight it, but with Trump in office, it's basically encouraged to "delete" your Diesel emissions equipment if you aren't in commercial operation.
…said deletion, which returns your truck to the state of the regulatory art circa 2009, also results in a doubling of fuel economy and about an 80% jump in horsepower.
These percentages seem a bit high compared to what I have seen. I usually see/hear about a 1-3mpg and 10-30% HP. I understand the point you are trying to make but "doubling of fuel economy and about an 80% jump in horsepower" is far from accurate, especially considering the downsides of a delete on every outside of the vehicle
shrug
Speaking from personal experience with a 2023 Chevy Duramax 3500, and a friend with a similar 3/4 ton Powerstroke.