I take my tools on the road often, so having the cases helps protect them and keep them organized in the Knaack or in the back of my truck.
If I never left the shop, I would possibly consider tossing the cases, but even then the cases are a nice organizational thing. Keeps the cords all contained, as well as keeps the bits, blades, adapters, whatever with the tool.
My old man kept all his power tools in a big cabinet with all the cords wrapped around the tool. It worked ok, and was a dense way to store the tools, but it was an organizational nightmare. Everything was piled on top of each other, and the parts were never with the tool.