Many good points being made here on both sides of the discussion, but I think it's a bit more than just home team bias. I think there is a lot of confirmation bias behind some decisions. That is team x is a top side and expected to win the game so is more likely to get the 50/50 decisions. of course it is worse when some decisions are just plainly incorrect. But it also happens with individual players eg. champion player Gary has been caught with the ball, but better be sure, lets give him a second or two longer to get rid of the ball. It happens all the time.