Sadly, that's what happens to concept cars.
I was following two late-model CUVs today. I don't know what model, but they were both white.
One had more pronounced cabin taper and the rear hatch on that one was maybe 2/3ds the width of the other.
One car with a lot of cabin taper is the Volvo C30:
https://en.wikipedia.org/wiki/Volvo_C30
I like 'em a lot.