What's crazier is that the process is so well defined, that I have a friend who needed a custom enclosure inside hardware he was designing, and because PCBs come in arbitrary shapes and size by default, it was much cheaper for him to use PCBs in his design than to have custom built enclosures out of other materials. This was for products produced in the 100's of units a month.
Indeed, PCB's achieved a high level of standardization and data transfer long before other processes came along such as CNC machining. It's been more than a couple decades since I ordered my first boards from a board house, but after they received my Gerber's, I heard nothing from them until boards came back.
In contrast, even today, sending any level of drawing to a machine shop at the time would have immediately resulted in a phone call to talk about exactly how I wanted something made, and why it couldn't really be made that way. While there are "quick turn" shops that can work directly from files, it's definitely a more recent development.
Even though "Gerbers" were a deeply primitive format, they got the job done.
At my workplace, one of the old-timers showed me the automated wire-wrapping machine, long since retired, on its way to the scrap yard.
