Yea, honestly today, I’m don’t know how much of the case that is, even today. At least not for simply printing.
HPGL has kind of been the de facto printer control language for a long, long time, and there’s little reason for it to be “reinvented”. Back in the day, you just opened the port and dumped data to the printer, and printing happened. For the simplest of use cases. Even the most advanced LaserJets would take raw text and print out 12 pt courier at 66 lines per page.
Similarly with Postscript printers, you could just “cat file.ps > /dev/printer” and pages showed up.
No, obviously, it’s different with scanners, page setup, faxing, and all that other modern stuff.
But rote printing, I bet it still works.
But I don’t know enough about USB as to whether you can just “cat file.txt > /dev/usb” and magic will happen.
There doesn’t seem to be a wide host of drivers in the linux world for a zillion different printers.
So, curious how that all works.