It's essential for the united states to be able to feed it's population. Keeping land fertile for farming and all the necessary supply chain intact is a national security issue.
It's a weird carbon offset for the fuel industry that isn't effective and it diverts huge amounts of farm land away from food crop usage. It ties farms to industry rather than supplying food, binding their profitability to the price of oil far more and that only exists because the US Gov mandates the ethanol blend.
It's supposed to be because it's renewable/sustainable using a biological product, but the industry is heavily dependent on synthetic fertilisers which come from refineries.
There are a great many reasons to get rid of the ethanol mix. Lower food costs being the biggest. Now that EVs are practical the need for trying to whitewash combustion fuel is overbaked.