I guess if you want this to change, you've first got to stop Iowa being so ludicrously influential in the presidential election cycle.

The last time the winner mattered was, perhaps, Obama 2008. The contested races since have yielded the following winners: Huckabee, Santorum, Clinton, Ted Cruz, and Buttigieg/Sanders.

From the article.

Though my understanding is that ethanol as a fuel additive is largely an anti-knock lead substitute. Alcohol was the originally-proposed solution, before the creation and adoption of tetraethyl lead. Apparent cost advantages drove the adoption of the latter. True costs proved somewhat greater.

My read is that the "biofuel" branding of fuel ethanol is actually a misdirection, though I don't have a good source on that.

https://en.wikipedia.org/wiki/MTBE_controversy

MTBE turned out to leach into groundwater quite readily and there was a pretty widespread outcry about it in the early aughts. Again, ethanol is a replacement (mentioned in the Wikipedia article above).

And yes, since anti-knock agents effectively slow combustion (and ethanol has lower energy-density than petroleum), net fuel efficiency is slightly reduced on a volumetric basis. Net effect remains better overall engine performance.