
There are plenty of surfaces in the average club or hall to bounce things around. But does that mean you should create mediocre mono sound for everyone to be fair to the folks who are seated under overhangs or behind the stage? I don't think so. (3) Room topologies vary, as do speaker setups.

FIX the balance problem that Mike says a stereo PA can create.

If I have a stereo PA, I can put the opposite side guitarist heavier into the mix there or in the front fills to compensate, i.e. This often means that a person standing, say, stage left will hear that guitar player often to the complete exclusion of the other. (2) A lot of places I work are fairly small. Just because you have pan controls on the individual instruments/vocals doesn't mean you have to use them. (1) Stereo effect returns usually sound a lot better than mono.
