We got our Insight not long after some other family members got a KIA-something (I forget what it is, I've even rode around in it but was wishing I had the Insight's interior the whole time from the seat fabric to the dashboard).
They noted it got mid 30's or something. Which isn't bad. But that's a highway figure, not putting around town.
Being as they live in BFE like I do, it will mostly see the Interstate or 55 MPH state routes whenever they want to go somewhere. So, in a way, it does make real sense.
But people who live around large metropolitan regions should really look beyond only the highway figure, IMO.
What's really notable is that cars in the 80's were getting 30's MPG. Safety features, this and that add up to the overall weight and improved engine technology has to be made to make up for the weight-gain. My old Accords in the 80's ALWAYS got about 34 MPG. Yup, even the carb'd ones.