I remember reading about "callers" in my early days of roleplaying. I only experienced it once. As a senior in High School, my group got invited to another group's game session. They were college students and then some. In other words, they were old.
When we got there I counted 16 people sitting at this really large table - 2 DMs and 14 player. I don't believe I ever rolled a die that night, but I do remember there were 2 "callers", one for each side of the table, more or less. Anything you wanted to do had to be announce via the caller.
I couldn't tell you what the adventure was about, as there was just a sensory overload going on, but I understood the need for a caller with 14 PCs.
I've never run a group larger than 10 (maybe as much as 12 in college - not 100% sure) but I dont recall my groups even having leaders let alone callers. Organized chaos for the win.
So, did you ever, or do you now, us a "caller" in your groups?