Your owners manual may specify the maximum percentage of ethanol..probably 15 % for use in the engine. Its bad stuff because it can cause corrosion..deteriate seals and gasketing , delivers less power and goes bad sooner if left in the tank very long..and then we pay extra for it because of added refining effort...you can thank our Federal government.
Fuel systems can be built to run on ethanol without damage, as they do in Brazil.. If higher ethanol content fuel ever becomes available here the retrofit business will be booming...
One reason to use more ethanol is so that we don't have to die in mideastern wars protecting 'our' share of the oil... that's the reasoning anyway (not necessarily mine)..