Good mileage has also a lot to do with weight/mass of a car.
Acceleration of a mass requires exponential input of energy, not linear amount of input. Moving a mass through air makes sure of that and aerodynamics cannot fix that, only partially negate it.
Friction on the surface that enables acceleration is always a problem, but you need it else you'll loose grip. And all of these negatives become more prevalent above 55 to 60MPH.
Stay below that speed and your engine can be a lot smaller and more efficient without giving up too much acceleration capacity. 50 to 60 miles per gallon is quite attainable even with current day tech.
And you'll get even more MPG's if you trade your lead foot in for a plastic one.
In short: people want their cars to go too fast too quickly and then complain that they have to spend so much on gas bills.
Every one likes to go to their destination as fast as they can, myself included. When you take a look at the amount of energy that has to put into your vehicle of choice to cut 5 minutes of travel time, or leave home 5 minutes earlier and see how money that already saves, you would be amazed.
That money you can spend on other fun things. Going fast is fun for me, so I don't mind occasionally spending money on that.
And there are also times when cruising can be just as fun, especially in a country where the average age is still under 30 years, has more women than men and summer practically all-year-round.
You learn to appreciate reggeaton music quite quickly over here, I can tell you that much. Oh, I almost forgot to mention that beer is sold in liter bottles over here...
