They kind of do, but they're only for high end cars. Imagine a big body Impala SS, rear wheel drive, with a small gas engine assisted by a hybrid battery. Or a 4runner that uses a big hybrid battery to generate a lot of low end torque. Maybe mate that to a diesel engine. Is there any reason why you couldn't get 30 mpg city in a big hybrid car/truck? The problem with small, economy cars is that they're small, they're tinny, they're low on power, especially when you load them up with people/gear. I think it could be done. Your thoughts?