Well insane conspiracy theory ranting and raving aside, the reason is because the EPA has changed the way MPG is calculated.
Previously the MPG on car window stickers was pretty optomistic if not downright impossible to achieve. Now they have gone to the other extreme, by adding additional drag, air conditioning, and higher speeds on the highway. It is now pretty easy to best the mileage listed these days.
To find real world MPG go to the various sites where they do test drives and extended road tests of the model you are looking at. Also, almost a truism across the board is that we have added horsepower to engines and faster acceleration times rather than gas mileage. You can do one or the other, but not both. In the 80's we were focused on mileage due to CAFE standards. By the 90's and 2000's it switched over to providing more horsepower.
There is a huge difference from what you 'remember' getting MPG back in 1985 when speeds were 55 MPH vs. today with much higher speeds and electronic equipment to power.