I think it was the other way around. In earlier periods, because we did not move around much and there was no radio and TV, people had a local way of speaking that developed separately from folk who came from over the mountain range, hill, river, lake, inlet or whatever.
A common language and pronunciation, free from regional dialect, has only been an issue relatively recently since the widespread use first of reading and writing, then successively of travel, communications, radio and TV as means of disseminating propaganda and the moulding of ideas and beliefs on a national and international scale. See also "Received Pronunciation".