The reason churches do this is the same reason schools feel the need to have TV screens in every classroom and computers for every student. Both churches and schools realize that words have very little power. Saying that a speech given by a teacher or a pastor has the same amount of power to engage people and persuade people as a rock band or a giant-screen movie or a video/computer game is like saying a single person can paddle a kayak from New York City to London and arrive before a Boeing 787 would arrive just by paddling fast enough.
Many people who overestimate the power of words are people like Veruca Salt in "Charlie nd The Chocolate Factory", spoiled brats who sincerely believe they can talk their way into or out of anything. And they will keep believing that until they, like most of us, someday find that they really can't. Everyone should at some point in their lives learn that there are times when their words have zero power. Here are some examples of when your words have zero power over other people:
1. They stare at you blankly, or like you're an escaped mental patient or an alien from outer space.
2. They turn away or walk away.
3. They look you right in the eye and call you a liar, or call you crazy, or claim you have no idea what you're talking about or what they've been through, or accuse you of not wanting them to have fun or be happy or be successful.
If you're going to straitjacket religious leaders and tell them the only tool they can utilize is their voice, don't be surprised when their congregation attendance drops dramatically and those leaders throw in the towel. The more you overregulate people, the more likely they are to give up and walk away.