I never understood why RJ-style connectors didn’t take off in the computer space outside of Ethernet and modems, which tend to be the most telecom-adjacent parts of the business. NIH syndrome? Thicc cable connectors convince people your $5k IBM AT isn’t a toy?
For low-voltage, low-speed stuff, it’s an obvious choice. I think pre-ADB Macs (128/512/Plus) used it for the keyboard, but there’s no reason we needed those awkward mini-DIN PS/2 and ADB cables that always involve fighting with orientation. Maybe even RJ-45 based serial ports.
Hell, why not design a RJ-style plug for USB instead of the joke that is full-size type B? It has an obvious orientation and a locking clip, and it’s about the same size. Don’t even get me started on SATA.