A big part of it has to do with bandwidth. The only way to provision that kind of bandwidth back then was coax, which costs a LOT more than twisted pair. For that reason, they could do point-to-point - from the Oval Office to the Senate Cloakroom for example - but couldn't build much of a switched network.
After that, it's nothing but an expensive novelty. Good for impressing investors, but not terribly practical.
EDIT: Hmmm, he says it ran on twisted pair, but I don't see how that's possible.