There are several horn flares that are designed specifically for dispersion control. Most designers are more concerned with directional control than they are with acoustic loading purely for efficiency's sake. That is definitely the current trend, the focus of modern loudspeaker design.

About loudspeaker arrays, when there are multiple point sources - which is what it takes to fill a 70,000 seat stadium - then directivity control and efficiency are your friends. One helps convert electrical power to acoustic power, and the other helps you put it where you want it without comb filtering and other anomalies.