Usually “cost savings”...utilizing the Internet for computer automation versus running leased ISDN telephone lines (or similar) for data into each pump station and control/valve point and the company offices is far, far cheaper. As to how they did it pre-1990’s/Internet I don’t know....not not a pipeline person. Maybe we have a FReeper pipeline expert here? I would assume many more employees and radios/phone systems??
re: “As to how they did it pre-1990’s/Internet I don’t know.”
Dial-up telephone lines. Even the early Motorola cell sites used dial-up telco telephone lines (with modems each end) for remote access for telemetry (not phone calls, but for monitoring, changing cellsite performance.)
T1’s to channel banks were used for the lines to/from a cellsite for handling the ‘traffic’.