How about the fact that DEF freezes at 12 degrees Fahrenheit, so in order to maintain it in liquid form it has to have an always on tank heater in winter. And if your battery happens to die for an unrelated reason in winter it can cause a thousand dollars in damage to the emissions system.

Or how about the fact that the regulations enforcing use of def cause you to be unable to use your vehicle after 500 miles of it detecting any kind of system fault. So imagine you are 10 minutes into a multi-hundred mile drive and an emissions fault pops up. By the time you get home you have about 120 miles of driving before you will not be able to start your vehicle. Now, you call the 2 dealers within 100 miles and due to a thing called the pandemic the soonest you can get a service appointment is over a month out.

AdBlue is enough of a pain in the ass that it is the reason I had to buy a second car. How's that for saving the environment.