Think about the environment it was originally used in — large organizations, computers which cost as much as a car, LANs which aren't easily accessible (e.g. the Unix people have access but laptops are expensive oddity and the sales people are probably sitting in front of a DOS box or shelled into that Unix server), etc. It's more defensible when your unix administrator is going to configure each of the servers to use the same NIS user directory.
All of that broke down when IP networking became the default, every desk in the building had a network port, and things like WiFi and laptops completely blew away the idea that the clients were managed by a single administrative group.