They are trying to keep lid on many facts.
1. They were trying to boost sales of cars of the Big three American Car companies but forgot to limit the program only to those cars.
2. Most of the sales are imports.
3. The dangerous hazardous waste produced by destroying perfectly good car's engines are a problem.
4. The benefits to those who take advantage of the program are minimal at best and the costs far exceed any benefits by a wide margin.
Other than that and maybe more it's working just fine.