I’ve noticed that this is a phenomenon that goes back to the 1960s among a lot of middle to upper class baby boomers from New England, New York, the Deep South and Florida etc. who have drifted away from their local accents in favor of the mid-western sounding broadcast standard spoken by the TV personalities of the day such as Walter Cronkite or Johnny Carson while their working class counterparts in the same areas have retained their forefathers way of speaking.
(cont. in the comments)