Jugga is right, the LSMs need alot of current as well as they create alot of electrical line noise. Line noise can be found heard through speakers like the crackle you hear on WTs speakers when it launches.
Also Jugga they can't always tap off of an exsisting line. Wire can only handle so much current based upon its size and ambient temperature factor. Once a main supply line reaches its maximum amp load, which is the sum of all things electrical at full amp draw, then a new line must be run.