There is a practical limit on how much ethanol may be mixed in with gasoline, before there becomes a problem with the separation of alcohol from gasoline during longer-term storage. Also, ethanol absorbs moisture from the atmosphere, further contaminating the fuel.
And corn or other grains are NOT the least-expensive way to produce ethanol. Using a fraction of natural gas, ethylene, and combining it in the presence of a catalyst, with water vapor, provides a good, reliable source of ethanol, of better controlled quality, than from distillation of alcohol from corn mash. However, this does not buy very many votes.
I have a radical idea: sell gas that is 100% gas. Novel concept, I know.