Searching the Internet it seems that the old automotive fuses were handmade and not reliable.
The Littelfuse company made several improvements.

1938:
A US patent was refused for "Little Fuse" because the words were too common.
The founder compromised by swapping the "l" and the "e" to form Littelfuse.

1940's:
Mostly worked to make devices for WW2.

1950's:
Started making fuses for television sets. They made the glass cartridge fuse we have used for decades.
A few automotive companies were using fuses at this time.

1960's
Automobile manufacturers finally got into doing a proper job of fusing.

1976
Littelfuse developed the Autofuse which was the first to make a blade-type fuse used in automobiles.

Today
The blade fuse has a built-in red LED to tell you when a fuse is blown. You no longer need to pull the fuse to see if it is blown.


SO! GM designers didn't think it necessary to fuse the antique/classic trucks we own today.
GM designers were also not thinking that one day, the cloth that covers our wiring, would rot and expose our twisted copper wires to oxidization.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."