I'm not sure what the point of 1/4" connectors would be given the rest of the audio chain.
I'm speculating: but I'm pretty sure that 1/8" jacks were the norm on computers because they had been the norm on consumer-electronics with headphone jacks (boom boxes, walkmans, etc).
Heck: in 1990 I was listening on a set of Sony studio monitors (great headphones, about $200 back then) that had a 1/8" jack on the end. I used an adapter (included) for my stereo gear.
It also shows that you aren't much from the computer world. Long before AOL had those phrases (AOL first became popular just after 1990): you had Amegia doing 4-channel wave-table synthesis and overdubbing of live video, with MIDI connectors, and yes, 1/8" jacks.