Back in the dark ages, when I was young, and cameras used an external flash the camera and flash used a PC jack. The Prontor/Compur connection goes back — way back — to the days of the Speed Graphic and beyond. Not quite as far back as “Flash Powder” but as far as I can remember.
My first camera, a Kodak Brownie Hawkeye didn’t have one, but everyone since then has. I remember seeing the “Hot Shoe” appear, but didn’t have a flash that took advantage of it so it wasn’t till recently when I finally upgraded to a Nikon D-50, then D-80 and a strobe to use with them that I became aware of the need for a better way to ‘Off Camera Flash’. The D-80 with a SB-800 capable of remote flash via Nikon’s CLS (Creative Lighting System) but not all flashes are capable of using CLS. Now I hardly ever use serious lighting with multiple strobes but I agree with David Hobby, aka The Strobist. Read his blog posting today to get a better view of what is wrong with the PC socket/cord and a modern way to operate remote flashes.