It is my understanding that Apple actually wanted to use 3.5mm jacks for their ADB keyboard/mouse interface in the early days, and some prototypes exist which used the jacks.
The plug manufacturers couldn’t guarantee that you wouldn’t sometimes get high resistance issues if the plugs were left connected all the time. On a pair of headphones you’d hear that as static and turn the plug or unplug/insert to get it going again. But you can’t “hear” through a keyboard.
It is my understanding that Apple actually wanted to use 3.5mm jacks for their ADB keyboard/mouse interface in the early days, and some prototypes exist which used the jacks.
https://www.applefritter.com/node/294
The plug manufacturers couldn’t guarantee that you wouldn’t sometimes get high resistance issues if the plugs were left connected all the time. On a pair of headphones you’d hear that as static and turn the plug or unplug/insert to get it going again. But you can’t “hear” through a keyboard.
They used mini DIN 4 instead.