This puzzles me, for several reasons. The concept is a handsome vehicle, and looks quite practical. It reminds me of a down-sized Traverse. I think it is an exciting vehicle that would compete well.
Other carmakers are already selling small people-movers with some success, such as the Kia Rondo, Mazda 5. More small MPVs are going to be sold in the U.S. in the near future, such as the rumored Ford C-Max (and possibly S-Max) MPVs based on the European Focus. Honda may bring the Stream here as well.
Maybe, for some reason, the economics didn't work out for GM. But from my seat, this looks like a mistake.