Why do galvanic cells req. two separate half cells as opposed to electrolysis?

[bentennason]

Is it because in electrolysis the ions need to migrate to each electrode?

[HERculina]

Due to the separation of half cells in a galvanic cell, the electrons formed from oxidation at the anode would be forced to move up the wires (ie. the external circuit) as it can not directly transfer to the other compartment/cell (the one with the cathode). Since a current is basically the continual movement of electrons, and the electrons are now moving up the wire, a current has been generated. Therefore, chemical energy has just been converted to electrical energy, which is the basis of galvanic cells unlike electrolytic where you convert electrical energy to chemical energy.

[ggxoxo]

I think you also need two half cells for galvanic because the reactants can react spontaneously

However, for electrolytic cells, the reactants do not react spontaneously (you need some sort of power supply to initiate the reaction); in saying that, the products will be able to react spontaneously and, hence, would need to be separated somehow...