Why did Orson Welles make character's dialog overlap?

In many of his movies, characters talk over each other. What for? Its so distracting. And most people don't do this in real life conversation because it is considered rude. He also made his characters talk offscreen. When the camera was focused on the main characters speaking. A different character was also talking offscreen (out of the camera's sight). What was the reason for these technique? What was he trying to convey?