Rubystars: "...I don't like the yelling style of black preachers. Why can't they just speak? Why do they have to scream everything? I could understand it perhaps, several decades back, but there are microphones these days..."
They are continuing with the same "call & response" communication which their ancestors in deepest, darkest, Africa used to do while in their natural native jungle environment.
The witch doctor or chief would shout some rhythmic "ooga-booga" jive, and the community as a whole would respond with more rhythmic screams, shouts, frenzied dances, spasmodic trance states, monkey noises, etc.
All that has changed is the religion of the participants and the continent.
It's what African Negroes do.