Because they can't come up with cars like this:
2009 Toyota Prius. Sharp looking. BETTER fuel economy than the current car, more power, slightly larger too. Toyota sold 41,000 of these in 2004. 191,000 last year. How many of these new Prius models will they sell? Their goal is one MILLION hybrids by 2010. I know I'll be buying one, or a similar car. I'd love to buy one from a US company. Apple computer can do it, why can't GM?
Chevy Volt. Yeah, OK. Toyota plans a plug in Prius by 2010 that gets 80mpg ++.