The puzzling thing to me was that it didn't even get very good gas milage. After numerous conversions, we figured it to get about 36 miles per gallon or so. I remember my mom's 2003 Honda Accord, with 160 horsepower and about twice the space, could easily get over 40 mpg.
The issue, I think, is that a car so underpowered actually becomes less efficient. Maintaining road speed with such a tiny engine makes you wind it up so much it's on a lousy place on the torque curve. About the only advantage is that they have to be dirt cheap to make.