Toyota's obviously on a hybrid run and doesn't want to expel the effort or expense of investing in diesel for the American market -- and having to overcome America's dirty diesel perceptions. The others, as mass market manufacturers, simply need more justification for the cost and complexity of oilburners in order to make the case for consumers to spend more.
Additionally, diesel's benefits are weighted differently according to EPA or CAFE standards. The EPA mileage numbers present diesels well, but CAFE's differing fuel mileage equation makes gas-hybrids look better than diesels, and CAFE is something all automakers are looking at. However, you'll notice that German brands aren't mentioned -- their price premium and European diesel volumes make a worthwhile case for diesels, so those diesel Jetta Sportwagons won't be going away any time soon.
[Source: Automotive News - Sub. Req.]