Thank our current administration in DC. They have pushed the EPA into phasing in very stringent new emissions standards which are aimed at SUVs, diesels in light trucks and eventually, heavy trucks. Fuels are regulated also. It might be possble for a manufacturer to design and certify a diesel for the upcoming standards, but would there be enough demand to justify the cost? Probably not. The situation is much the same as it was for gasoline engines in the seventies. Anticipating these new standards is one of the reasons MB introduced their new series of gasoline engines. Perhaps as the technology is developed MB will reintroduce diesels, but don't expect them any time soon.