Language is our biggest social connection .
We may like to believe that people can move up the social ladder but often even financially successful people are not accepted by their peers because of their regional or lower class vocabulary. I believe there are companies that teach proper diction and improve language skills for professionals that are being held back because of racial or social or regional accents.
One would think that TV would help to eliminate regional and class distinctions, but social group has a much larger impact.
You're right. TV has almost no effect; otherwise all of us would be speaking with the Midwestern accent favored by the producers of TV programs.
Indeed, your speech accent is formed by the people you grew up with.