A 4 piece kit looks boring on a large stage, there is an entertainment factor in there as well.
Also, he doesn't have to set up this kit himself or carry it or pay for it....lol.
A lot of the drums he uses are close in range to each other tone wise, he could stand to knock off a few.
I don't think you can distinguish between some of the toms because they are all larger sizes.
I just looks so cool and I am sure it is real fun to play and to be surrounded by drums.
It is less scary with a big crowd, when you have a lot of drums to hide behind...lol.