It’s not a regional thing, Luckygirl. It happens everywhere, but unfortunately makes the speaker sound ignorant.
I do think children ought to be taught how to speak. There are some people round here (near Liverpool) who are incomprehensible. In many other places, too. It puts them at a huge disadvantage, but many don’t realise that. It became fashionable in the sixties to pretend it didn’t matter, but it does. Not as much as it did, but good clear, correct speech will help in life.
I have a friend who taught music in a small private school. The teachers were not allowed to ‘correct’ the children’s speech, but she made the point that in a choir everyone has to pronounce the words exactly the same or the sound is very messy. Standard RP is normally used by choirs. The head conceded she was right, but she still wasn’t allowed to correct their speech except when they were singing. Why not?