Perhaps we do, if any of the mass of American boobs decide to actually think through an issue. Part of this remedial education starts with the knowledge that CAFE standards are generated by work of the NHTSA. While they provide extensive analytical review, they are tasked by the administration to look at factors and goals that may or may not have been looked at in prior administrations - choices that can affect outcome.
Frankly, I am not familiar with CAFE work after 2009 (the last time I investigated it) BUT the standards proposed (and passed) by the Obama administration back then is illustrative of how it works.
In a nutshell: under Bush the NHTSA in 2008 analyzed the recommended 35.5mpg in 2016 as the goal, with light Trucks to his 30mpg by 2016. The Obama Administration used the same analysis, but chose to propose another option, to increase the standard to 39mpg (there were four).
Using models, the NHTSA evaluates the safety, fuel efficiency, environmental benefits, and economic costs. In this evaluation there are tradeoffs; e.g. smaller cars mean better MGP but lower SAFETY.
The difference between the Bush proposal and the Obama proposal was not over methodology (they were identical) but over deciding what goal was "best". The Bush administration chose the economically most logical goal, that of maximization of social benefits over the social costs imposed by regulation (SB minus SC) from regulation.
The Obama administration chose to propose even tougher and more costly regulation, so tough that the social net benefit was eroded to the point zero return. TB=TC.
You might think of it this way, there is an inflection point where for every dollar of added regulation you are LOSING more than you are gaining. (EG losing jobs, consumer buying power, etc.).
In my view, the Obama administration choice was not based on the gain to social well being, but the quasi-religious and subjective belief that 'more economy is always better'. But the net result of that policy was also predicted to be an additional loss of 37,000 jobs and microscopic benefit in the reduction of greenhouse gases:
https://keithhennessey.com/2009/05/19/understanding-the-presidents-cafe-announcement/
So as most economists and economically literate know, especially in regulatory economics, there can be too much of a good think.