Indirect taxes hit the corporations every step of the way. Even the extraction of the raw crude from the ground is taxed. They probably tax the exhaust from the vehicle's engine seven ways. Everybody pays, sometimes in multiples.
Beside getting better MPG, we'd not need those darn cat converters which eventually clog up and ruin engines by gradually backing excessive heat up into the lower end of the engine, melting the Teflon coating on the lowest piston ring ( the oil scavenging ring).
The loss of power, etc. develops so slowly that most people just want a new car with pep & zing, like when their car didn't have a clogged cat. You'd almost think someone wanted it that way.
I'm cynical about this because I grew up next door to an automotive research center where alot of this type of intricate planned obsolescence was developed & perfected.
Knowing & seeing first hand how much time and effort was put into this aspect of automotive deception, I can only assume they left few other turns unstoned.