There are great differences between, for example, Kansai Ben and Kanto Ben, all of which may be disappearing
Here is a story about a friend of mine which might explain what I mean.
He was from Kanto area, in the eastern part of Japan, and was staying as a lodger with a family in Kyoto when he was a student.
Every day the lady of the house sent him off by saying, "Ohayo Okaeri yasu" (as is or was always the case with people in Kyoto). The literal meaning of this is "Come home early" or "We expect your early return home this evening." "Itterasshai" is used in standard Japanese.
He had never really noticed the expression itself, still less its literal meaning, as it was merely one of the daily greetings.
One evening he went to a drinking party and came back after midnight, which was quite late given the circumstances of the time. He felt quite guilty about this since he was afraid he had put the family to some trouble.
So, the next morning the hard-working boy was leaving for school as usual, despite returning home late the previous night.
As usual, the landlady said "Ohayo Okaeri yasu". Suddenly the boy noticed the phrase and his feelings of caused him to analyze the meaning of the greeting, which he had always heard since the beginning of his time in Kyoto but had not actually noticed.
So he wondered to himself: "Um. Did she say "Come back early" because I came home late last night?" "Is this the same greeting she's been using since I came here?" He
was quite uncomfortable about this difference in dialects for some time.
It's not a great story, I know, but he laughs himself to tears when he tells it.
Anyway, that was long ago now.
I think that the various regional dialects are slowly vanishing and being replaced with the Japanese spoken on NHK television in most places.