One of those mysteries in life sadly regret I won't get an answer to.
But one answer I know, the famed IMSAI 100, the first microcomputer so famously on the cover of Popular Electronics in the 1970s, had a 100 pin circuit board, the famed S100 BUS. People wanted to know WHY? the performance?, the architecture, the technical reason why the creator chose this bus. Final answer: Because they found a bunch of surplus military S100 boards and that's what they used. ^)