As someone who grew up in Appalachia, there are certain biases that come with that accent. It's is one of the reasons some professionals from the region try very hard to "talk normally." There is even training you can undergo to lose your accent.
I learned early in my career that people make certain assumptions about you based on your accent. Over the years I have unconsciously developed a "public speaking accent" that is quite a bit different from how I normally talk. I've been told I sound generically Midwestern when traveling or giving a conference presentation (one person even said Canadian.) I didn't even realize I was doing it until one conference when someone pointed it out to me at a bar-track later in the evening.
Though I assume he didn't mention that his family had been fairly well known off course bookies (pre legalisation)
Visiting NYC in 2018 and 2019 made me realize that that phrase is literal. There's nothing like walking down the sidewalk only to have the guy in front of you just stop to gawk at something with no warning, forcing you to stop short or swerve on a dime to avoid bumping into them. Or maybe if you're lucky they didn't just stop short, they'd already been just standing there in the dead center of the sidewalk since they came into view, but you still have to go around them.
After one afternoon of walking around the city, I already felt like shouting "Hey, I'm walkin' here!" several times.
(and being a tourist myself, I was actively self-conscious of whenever I wanted to gawk at something, so I always made sure I moved to the innermost part of the sidewalk and put my back to a wall if I ever wanted to stop and look at something or pull my phone out)
That being said, especially in rural areas, the dialects are well kept. In fact, being from the western regions of Germany, I have a hard time understanding villagers from the Black Forest if they talk their native dialect.
Still, in urban areas, the general trend is the same, no ? Dialects are spoken by less and less people (in fact I don't speak a single word of Plattdeutsch, even if I'm from an area where it was once common). What remains are temporary sociolects and accents. At least that's my perception of things.
The most prominent example I can think of is Cardi B. She has a heavy Bronx accent, and will say “talk” and “walk” in the old New York manner of “tawlk” and “wawlk”.
I don't have the exact source but I believe research has shown the opposite. When cable television started becoming more common about 20 years ago, there was a belief that a common "source accent" would flatten out regional differences in accents. Apparently, it has made accents more distinct as people, consciously or not, were using those accents as a "tribal marker" to differentiate themselves from the rest of the country.
On a broader note, I remember reading an OpEd in the late 90's that predicted that because people were going to be getting all of their information from a common source (aka the Internet) that it would eliminate debates between regions of the US. The idea was that with shared common information, we would all have shared beliefs. Obviously, this completely missed the ball with regards to personalized streams of information (e.g. Netflix, Pandora etc).