Why do many domestic TV dramas and movies have to be dubbed again after filming?

Yes . . Well, it's because the actors actually speak during the filming process, and the video sound directly taken by the camera is not very loud, and the Mandarin of many actors can't be said to be an absolute standard, and the voice line can't be said to be absolutely suitable for that role. Later dubbing, feelings may not be as rich as at the beginning. So the voice actor is a person who works hard behind the actor. Also, if it is a transnational Sino-Korean cooperative TV series or Cantonese in Taiwan Province Province, we can't understand it-(hope to adopt it)