An enclosed chain is an interesting idea...interesting retro idea, I guess I should say. Never saw one of the early Hondas with it; but I had seen reprints of the ads.
But. Even enclosed, there's wear on the sprockets. Ask anyone who's had a camshaft chain fail.
I agree with others, how we're not going to see the midsized shaft-drivers again; and I agree with the given reasons why. The added cost and complexity in tooling, didn't translate into additional sales...why bother? America is not an important motorcycle market - relatively speaking. Not anymore; not the way it was in the 1960s. People were more adventurous and had less income; and, frankly, there weren't nearly so many cars per person and so good used car prices stayed up. Back about 1965, a college student was going to have to take the bus; and a little moped or cycle could be liberating. Today, with borrowed money so free, most of them have cars. Many since high school, even.
So...we get what's easy, inexpensive to tool up, and what the market demonstrates buyers will accept.
In fact, every shaft model Honda brought out, was less than a success except for the Gold Wing and to a lesser extent the CX500. Everything else seems to have come, not sold quickly, and went away forever. Now it seems the Crosstour is going the same way.