gotta take care of the horses and the armor and weapons.

squires and stable boys and whatnot support staff.
What about the knight's family. He's gotta bring home the bacon to a wife and a kid or two. and maybe some of the staff have a family member or two

so for each cavalry on the field there's 8 people back in town that make it possible


just trying to come up with a rationale. personally I think 9 is too high. but meh. I'm sure it's for game balance reasons