My theory is that they made so much noise it made it very difficult for the players to communicate - I sit just 5 rows from the pitch in the East stand and the 'white' noise made it almost impossible for me to hear what the person next to me was shouting.
I wonder how much of the drop in 'atmosphere' at grounds has occurred due to the modern obsession for singing. I didn't join a choir when I started going to football matches over 50 years ago!
Fans didn't use to burst into song when their team scored but the noise in the ground was basically...