There’s probably a rule or something that says the entire kit has to be different. And if you’re in a scrum with your head down looking at the ball, you’re not looking at the other players jersey colour so different socks is how you tell team mates apart.
As an actual game it was pretty terrible. Unique skills only being learnable by a single person, multiple nested menus to perform basic functions like equipping something, lots of questionable things like overtuned traps and trap rooms in low level areas.