As pointed out they are, but the market will not really pay for them.

The manufacturers make more profit on large higher performance vehicles, and have had to sell their smaller high efficient vehicles at a loss for years to meet their fleet efficiency standards (CAFE requirements). It does not cost 3x as much to make a $90k car as a $30k one.

So the typical efficient car buyer is not really interested in paying for efficiency, they are buying on price.