The DR Z400SM is still in production, it just doesn't come to the US...if I'm not mistaken it's available in Canada.
Honda has four street legal Supermoto models to choose from in Italy....
The Dual Sport segment has never been a large market in the US and the Supermoto market is an even smaller portion of that market. The manufacturers tend to put bikes in regions where the sell best, or least better. Back in the mid eighties Honda's Dual Sport lineup had five or six models to choose from. At that time sport bikes were just getting popular and the demand for those increased and demand for dual sports dropped off. For a long time it was just the XR650L, then the CRF230L was added and they just added the CRF 250L. Hopefully this growing lineup will continue to grow, and hopefully new SM models will follow.
As far as practical goes I built my DR 650SM purely for fun in the twisties. I took what is (and will always be) a heavy big bore single that is not particular nimble off road...the tighter things get the worse it becomes. It does do everything satisfactorily and nothing exceptionally. Converting it into Supermoto form gave me a light weight bike (by street standards) that handles pretty damn good and sticks to the road like a magnet...the tighter things get the better it is. Converting to SM made a mediocre bike much more fun and focused. I put a small roll bag on the back so I can ride with empty pockets and have a place to store stuff when I'm parked...and I have some storage space without hanging a set of samsonite matched luggage off the sides. I hope to see more street legal Supermoto models in the future because this bike is the most fun I've ever had on the street.
I believe this is a picture of the 2012 Canadian DR Z400SM