Prior to the advent of the Microcomputer (of which the Personal Computer is a subset), computing meant getting a slice of time at a communal computer. Wait in line, sign up, book your time at the console; adjust your pocket protector while waiting. Multiuser was the rule because these machines were so costly to make; computing was primarily an institutional phenomenon, complete with its own institutional gatekeepers.
A limited analogy: in the early days of computing, practically all you could buy were the equivalent of buses, built and designed for carrying people. Only the rich and the crazy would have bought such buses for personal use. In this analogy, when the PC came along, it was like suddenly finding cars for sale on the bus lot. And they were a fraction of the cost and comparatively user-friendly.