When the Voyager missions were launched most of the world didn't have international calling. So making a call from lets say Somalia to the US, involved finding a post office with the only international line in town and "booking" a call. Which meant you had to walk over and write down your name (and if you were lucky enough to have a local landline your 4 digit phone number) in a ledger and then walk back home to sit by the phone, for two days to a week, before the operator would call up to tell you the line was available. If the exchange wasn't sophisticated enough to forward the call, you then had to drop everything you were doing and walk back to the post office to use the line. Now think about how anything worked with that level of latency :)