I would have to add that my sister and brother in law have heavy southern accents....their kids...not so much....many Southerners are shamed if they go to college and have a Southern accent...just my observation...One is an attorney and the other is an engineer...College beat the accent out of them.
I think they mostly can’t help it. I left home when I was 18 to go to school on the west coast. By Christmas I was shocked to hear my Dad had picked up a mid-western accent. Of course he didn’t. I was the one who had changed. My ears were hearing something different for 3 or 4 months and all of a sudden it stood out.
I was also teased endlessly for how I pronounced my vowels. Apparently I drew them out. I listened to the laughter but I could not hear what they heard. The joke went past me.
A friend traveled west to see me. I drove her home. As we were driving one night she said “Look, a woof...” I said, “A what?” She said “A woof..” LOL. I laughed pretty hard at that one.
The west coast has their own bad speech habits. They are more to do with what used to be called “valley girl” sorts of cultural talk than they are accent. I bet a professional would say they too have an accent that is all their own.
All regional accents in my observation are becoming less noticeable among the young. I do not think it has to do with college, but more a result of mass communications in today’s world. Accents are acquired from ones peers more than ones parents. When I grew up, my peers were located pretty much in my regional area, the NYC area. I have a noticeable Irish NYC accent. My kids peers with the internet and all is a much wider area than what I experienced, thus they do not have a strong NYC area accent, even though they live in the same area I grew up in. Accents are acquired in ones adolescent stage, and will lessen if you move out of the area you grew up in. However, when you reach senior citizen status, the accent of your youth will creep back in. For example, my grandfather was born in raised in the north of England. By the time he was middle aged, you would have thought he was born in Ohio. In his seventies, the old accent came back to an extent, and really came back when he was angry.
I had a Yankee once say to me, “Oh, you don’t have much of an accent at all”, in an approving tone.
I said, “Well, thanks for telling me. I guess I’ll have to work on that, won’t I?”