If you don't understand why that was ever a thing: This comes from a time where in networks (and, to some degree at some point, the entire Internet), basically only non-administrator users were not trusted. Besides this weird idea of "privileged ports" that would prevent a non-administrator user to pose as a system service to other computers, it was also entirely common to just use IP address ranges for authentication.
It was an entirely different world. The thought that someone rogue could plug in an entire malicious machine into a network, rather than just being a random student having user-level access, was present, but often not considered a serious enough threat. And it may not have been, given what a lot of networks--and computers--were used for back then, compared to today.