Cash for clunkers was an indirect pay off for union support of the criminal enterprise party. If inventories were not reduced quickly, many union slugs would have been laid off. It was also a fascist way to inject the federal oligarchy into more of the nation’s life.
And it was a stupid waste of resources too. People’s usage of an automobile varies greatly. A cheap gas-hog clunker might be the ideal thing for the proverbial grandma who only goes to church on Sunday and grocery shopping on Wednesday. Or for the person who works nearby where he lives. She appreciates the protection of the land yacht, and does not use much gas in total. A Prius would be wasted on her, assuming she could afford it. Letting the clunker be traded in and resold was more energy wise than destroying it.