This was before broadband, and access to external systems was done through a device that connected to...a phone. Your local calling area would be maybe a 30 mile radius or so (it varied a lot depending on local carrier). Wanna see what's on that mainframe at the university 100 miles away? Well, be quick because it's going to be pricey. Or...
How pricey? Someone else already looked it up, but I recall MCI advertising long distance calls for $0.10/minute. That's $6/hour. Minimum wage was something like $3/hour. So if you're a kid working at McDonald's, you needed to work two hours for every hour of access. Or...