Doesn't suprise me. My wife is from a rural town in NC, and was told by her high school teachers that she needed to lose her southern accent if she wanted to be taken seriously in college. When she was working on or master's degree in Maryland, a writing professor commented "you speak and write so well, I never would have guessed you're from the south". That kind of discrimination is very prevalent in academia and me…
I grew up in Staten Island, the son of a couple of Brooklyn Italians. As a kid I had what I now hear as a comically heavy Brooklyn accent.
As a middle-middle class kid surrounded by other kids like me, I considered my accent normal. As I got older and was exposed to people from outside our little bubble, I began to notice their reactions to my accent, which were always in jest but affected me just the same.
Hearing their jokes and their own accents, I began associate the 'standard' American accent with upperclassness, which I wanted to achieve. So I consciously worked on my accent over a number of years. By the end of high school, my R's were nearly properly rounded. By the end of college, my accent had almost completely gone. Today, it is 100% gone. I speak like a journalist from Ohio, except with more swearing.
In many ways, I miss the accent. I feel like an outsider wherever I am, whether it's at work (where I feel like I'm playing a part to fit in) or at a deli, buying a mortadella sandwich, where it feels like returning to a place I've left. But 'fixing' the accent has undoubtedly made it easier for me to advance my career.