Rotor Arm internals - why carbon vs. hard wired?
 

I always assumed that rotors were solid metal on the inside, and that the contact point was one piece of metal from the center of the rotor out to the tip of the (I know it is in older cars) I cut an old 911 rotor arm in half and it looks to be solid carbon in the middle of the arm, between the top of the rotor and the metal contact point on the tip. Why not a solid piece of metal?

^^^^^^^^^^increases high voltage resistance which, in turn, decreases static discharge^^^^^^^^^^^this is needed to avoid electrical interference with low voltage equipment such as computers, radio's, etc.

Yes, increases resistance. It's part of a system of managing secondary circuit resistance. Other places resistance can be introduced is in the wires themselves, in the spark plug connector, and in resistance plugs. You need to be careful to use the system that was designed for the engine. You don't want to have a resistor rotor, resistor plugs, resistor connector, and resister plugs.