Some of us do. ;-)
Another advantage of DCTs over manuals is that they're easier to control by the car CPU. Presumably one of the things the car manufacturers are thinking about is "economy" modes where the throttle and gears are automatically selected to maximize efficiency. One can do that with a manual too, e.g. old Corvettes that shifted themselves into ultra-overdrive to get 20 mpg (or whatever), but people expect manuals to be manual and don't like it.
I think the US fleet is too big for most cars here to be diesels. I don't think there's a way to change the fuel mix to get enough diesel for another 150M cars. Could be wrong, though. Refineries can adjust the cracking mix to some extent, and the cracking depends on the qualities of the starting crude, but you can't (easily) go from, say, 20 gal gasoline per barrel with 15 gal of diesel to 30 gal of diesel and 5 gal gasoline.
http://www.theoildrum.com/node/6089
Efficiency all around is the way to go.
Cheers,
Scott.
