Why do accents vary from place to place? Did the water change them, or were they influenced by their parents since childhood?

The answer is "water". Why are fruits and vegetables delicious in some places and not in others? It is because the soil and water quality are different. The same is true of human accents. For example, "gaomi city" and "Jiaonan City" in Shandong Province are on the same waterline with similar accents, and the people in the villages connecting the two cities have similar accents. I am from Gaomi. I used to go to Jiaonan to buy seafood, and I was confused. Later, I asked a lot of people and finally figured it out.