The most important part of A/V in a House of Worship is getting the message across. They want to put a message out about the liturgy and failure to deliver this message would defeat the purpose. The message going through the A/V system needs to be intelligible. This mean more than just speakers that are loud. Acoustic treatments cut down on reflections that decrease intelligibility. When you have sound coming out of the speakers reflecting off a wall, the sound arrives at different times, making the message unintelligible to the human ear. Treating the walls helps keep the sound coming.