Probably has something to do with the pillars and the height, and that people buying minivans generally want that extra rear cargo space.
I personally don't like hatches at all, especially not on sedans that come in both hatch and non-hatch versions. I know people appreciate the extra space, but I don't like the look, and never agree when someone says x or y car looks better as a hatchback than a sedan with a trunk. I do think there are plenty of cars that look okay as hatchbacks, just not better. It's not practical for all vehicles to be fastbacks, but that is what I like best out of all the design configurations, though you usually will get less trunk space than something more practical.
It's a matter of preference, though. It's like preferring, uhh, a very large derrière on a woman on not.
