Way back in the Dark Ages (tm)... High School, late 70's, AD&D. Four players rotating GMing. We each ran five characters, each having our own Cleric, Wizard, Thief, etc. The entire group, plus henchmen and followers travelled the world in a big fleet. When we got to the Dungeon or area where we were adventuring, the three players would each select two characters to make up a party of six PCs.
Played a CoC campaign that ended last fall. 1920's England. Three of us (out of 5) played 'secondary' characters. Two of them were servant/driver types, mine was a military liaison/contact type. All 3 were somewhat 'lesser' than our main characters and subject to Keeper (GM) intervention.
Played in a few large games over the years. Used to be that six PCs in a party was fairly common. Then 3e comes out with a standard party size of FOUR, which absolutely floored me.