New car mileage

Why do newer (relative) cars get shitty gas mileage, Ie. 2010 PT Cruiser 19/24 mpg? Really, that's good slant 6 territory. Remember the Plymouth Champ, that sucker was 50mpg with an old fashioned carb! Browsing cheap used cars and just shaking my head at the posted mpg. 19 mpg for a Toyota 22R truck? 28/38 for a VW TDI is more like it but I remember the 'ol Diesel rabbit got 50+. F the creature comforts, dont need 'em.
The auto industry doesn't want the vehicle's to get good mileage