[Shrocat]

From the time Henry Ford built his first assembly line, until the oil crunch of 1974 Detroit was able to get away with stuff like this. American auto makers had no foreign competition until the 60's, and that was pretty minor until the late 70's when the Japanese started to import real cars. They were hit hard in the 80's but apparently never really learned the lessons that they needed to learn to get out of the hole they had put themselves in.
Post WWII Detroit based their marketing on people replacing their cars every 4 years. And they had no need of worrying greatly about cars lasting longer than that. On the other hand, cars today are lasting longer, for the most part, than cars of 30 years ago.
To have a car last 150 to 200 K miles was pretty good in those days. Now, they routinely go over 200K miles.