From what I understand, not all vehicles are designed to handle E85.  If the government would mandate that all gasoline vehicles would handle E85, then the consumer would have a choice as to which fuels they use.   My understanding is that having an engine designed for E85 may mean a change in types of gaskets and rubber components used, and maybe some tweaks in the computer software.  That is my understanding.  It seems to me that all vehicles should have this done.