We have been wondering why they aren't producing the mega efficient vehicles like they were able to in the 80's. The only conclusion that we could come up with was the extra weight from extra safety features like airbags and stronger frames.
In 1991 we purchased an Astro van. I am still driving it. It gets 21-22 mpg highway and 18-19 city. I can still tow our trailer and the interior is still in good condition considering its age, and the amount of use that it has been through. After 287,000 miles it has finally developed a problem with a gasket leaking on the trans. This is the first repair to the trans, while the engine has never been touched. The rear end developed a problem about 100,000 miles ago. I so agree with the article, you would think that with the recent advances in technology, we would have come much further in the development of more fuel efficient vehicles.
As well as the federally mandated safety content, there is also the market mandated luxury content. This is a more affluent country than it was 25 years ago. Very few shoppers will settle for a slow, noisy car with no AC. The ones who will won't pay new car prices.
Regarding claimed mileage, you can't compare 80s window sticker numbers to modern cars. The EPA changed the test to give lower results in 1984, and again in 2007. 50 then would be about 35 now.