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.
I knew that when I bought the 87 Caprice. 60,000 mile warranty. No problem whatsoever until 61,000 miles, then all the tin parts started to come apart. Those automotive engineers know their stuff, no question.