I had that discussion with my son at the beginning of this season. There are no theatres working, no concerts happening, speakers and audio equipment are unused and available.The wife has just asked if they play the crowd noise for the players in the stadium so they feel more comfortable.
My thoughts are that someone tried it and it just didn't work. The empty stadiums need physical bodies in them to help the sound bounce around and bouncing off steel, plastic and concrete alone just does not work. If they didn't even try it then that is criminal.
I can't watch a game without the fake crowd noise, it must be soul destroying for the players.