I've noticed this for years. It's especially true for the best seats, those on camera right behind the plate.
Record a game and freeze the replay as the pitcher is releasing the ball. I'll bet more than half the people you can see are not watching.
Of course, they're bored out of their minds as every nobody who comes to bat walks around after every pitch. We're so far removed from those half-hearted reforms that Commissioner Manfred, the A-Rod Slayer, never even attempted to enforce in 2015 that TV announcers rarely say anything about the lack of action, which is only compounded by all the strike outs resulting from increasing percentages of fastballs travelling at faster speeds.
And after being bored for four hours, the dopes in attendance must get home when the game finally ends.