In the Western US, in particular, the cost of lost wages and other related economic costs due to increased travel times outweighed the fuel savings. Then, the predicted fuel crisis didn't materialize adding even more reasons not to drive 55.
It's much the same thing with masks. There is no clear evidence they helped in any substantial way, but the cost of them along with other mandated actions caused an incredible economic loss to the nation. Now with no new wave of China Disease as predicted, and the population increasing being vaccinated, the mask mandate has completely outlived its usefulness.