A lot of casters who are good players do this because it's a habit good players pick up. If you're good at the game there's no reason to watch all the pretty explosions - once you know what's going to happen, you look away.
I thought that also and i get it. It is normal to do that.
But it is a cast and it should show the beauty of the game and the fight, right?
P.S. Thanks for the replay Dane!