The 11" perhaps didn't have the ROI to make it worthwhile but we'll never know.
Could be the case.
Thing has/had some longevity in terms of both life and popularity, though, hasn't it?
I know we probably see a disproportionate number of fans on this particular forum, but was in the commons or food court area of the student union at Indiana State the other day and saw some kids using the Air, including at least one 11-inch.
For a computer the experts have been predicting dead for quite a while, it seems to be a busy little zombie.
Maybe the folks at Apple at some point said something to the effect of, "We've got to stop making such long-lasting, popular units, or we'll never up-sell these people!"
I was working for a small news service when I first used an MBA, an 11-inch company issue. First thought was, "This is my main/only computer?" After a year, I was thinking, "This is probably the perfect computer for a writer on the road."