Michael:
The origin of the 8P8C plug/jack in mainstream use came long before data ran on anything but coax. AT&T's systems in the early 1970's required three pairs, sometimes four for long runs on their electronic sets. They set up their own pin assignments, one for voice, one for data and one for power. Again, this was years before 568A/B was even on the drawing board.
I would assume that since AT&T systems were dominant in many major markets, their wiring became the "standard". Their wiring pattern is what is known today as 568B. I would imagine that if their systems hadn't been developed with this wiring pattern, 568A would be the only standard today.
I guess the simple answer is that the concept of LANs as we know them today didn't exist back then. As they today's LANs developed, they were adapted to work in harmony with what had pretty much become the wiring norm.
