It's like the nose on your face. You can change it ever so slightly, but there's not a great deal you can do with it. But accents characterise a person, often unfairly. And their associations change. Brum sounds miserable.
Cockney sounds devious and aggressive.
West Country speakers, among whom I proudly include myself, sound like simpletons. Some RP speakers complain that their accents make them the subject of prejudice. But those with pronounced regional accents have always experienced that. I know this to be true, because I'm only just getting over it. In its upper-class form it is none of these, being full of irrational elisions and slack articulation.