I wonder if it has something to do with the kind of person who would buy a HCH vs. a Prius.

The HCH blends in.
The Prius stands out.

I think the buyers have different profiles and driving style may be a part of it.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.