A basic knowledge of music is important for the sound system operator unless only speech is amplified. When running a sound system you should consider yourself the “mix musician”. You will be balancing the musicians against each other and determining how the congregation hears them. As such you are an important part of the musical group, and need to understand what is important for music to sound good.
This does not mean you have to be able to play an instrument or read music (although that could not hurt). It does mean you need to understand some musical concepts and be able to speak the language of music in order to properly communicate with the other musicians in your role as the mix musician.