The short answer

Q: "Why does the government want to destroy your automobile's engine?"

A: Since the Gummint now has its fingers in the game of auto production, they'd like to sell you a new car in the shortest possible interval.

If the shoe fits...

I'm not entirely sure that's the case, actually, as the situation, as I'm seeing it anyway, has been a Pandora's box, with the expected result of creating more problems than the inclusion of ethanol in our fuel could ever solve. Government has a long history of ignoring the immutable law of unintended consequences, and this instance is really no different.