Motoalliance plow/winch combo issue/question

So after forking out $1,100 on the denali plow setup and 3500 winch from motoalliance I find out I need whats known as a "bus bar kit" to install it. Apparently Warn winches come with this. I specifically asked before I purchased if I had everything I needed.

Another $100 for the bus bar kit… what is this? And why wouldn’t they sell it with the kit