Bert... whatever the reasons & origin, "BBC English" is a way to create a commonly understood, basic dialect since travel by powered vehicle, then radio, then television, then internet...etc., have made it at least useful and almost necessary for all areas to communicate easily.

My wife told of traveling in England 35 years ago, and having a waitress 'seem' to not understand when asked for a glass of 'water'. Finally, she perked up and asked: "Oh...you mean woah-tah?"
Now that may have been an 'attitude' rather than a real confusion, but it does point at the need for any person in any country to at least be able to approximate a basic accent and vocabulary, no matter what they use at home or in their neighborhood market.

(Years ago, I heard a black woman activist interviewed on the radio about "Black English" - at that time called Ebonics. She insisted that it was a genuine language, and that black children should not be shamed or pressured into not using it...and that it should even be taught in school.
   Fine....except that the woman explained all this in perfect 'regular' English, and made no mention of how African-American kids would compete in job interviews if they spoke ONLY Ebonics! I have no doubt she 'could' drop into Ebonics when necessary, but she seemed to have no concern about others being able to get out of it.)

If it is a matter of being essentially bi-lingual....fine. I have NO objection to anyone, anywhere preserving their childhood language and using it at home or even 80% of the time in their area. But for easy access to all the benefits of complex society, there needs to be a common way of communicating, even if touches of accent remain.

(An American Senator from Alabama, Howell Heflin, had a pronounced southern accent, and was known for using the most extreme, hard to understand, form of it to irritate colleagues when he wanted to bait them.)