I've wondered that myself. Either they were all just smaller than we are today, or the designers were too scared to suggest big changes to the market too quickly.
In the late 1930s John Deere hired a man to "style" their tractors. I believe his name was Dryefuss. They offered both styled and unstyled models for a couple years because they thought farmers would be less likely to buy dolled up tractors. A tractor is a purpose built piece of equipment, so why would a farmer, most of whom were living on a fairly low income, want to pay more for a prettier tractor?
I suspect the narrow front designs with large individual fenders was a product of similar thinking at the time. People were used to cars looking a certain way and a major change wouldn't have been well received, or make enough revenue to cover the design costs. Look at the Chrysler Airflows as an example: it was simply released before it's time. Too much change too fast. But, if you make gradual changes year after year, the concept eventually stops being the exception and becomes the rule instead. Modern cars are built with comfort as a leading design factor, 80 years ago function was much more important than comfort. But, in my opinion, that way of thinking made for a much more attractive looking car.