Why does the cathode have to be made out Cu in a Zn-Cu voltaic cell? The classic voltaic cell has a $\ce{Zn}$ anode and $\ce{Cu}$ cathode. The reduction half reaction occurring at the cathode combines aqueous copper ions and electrons supplied by the anode to form solid $\ce{Cu}$. So what is the purpose of the $\ce{Cu}$ cathode? $\ce{Cu}$ is produced anyways from the electrons supplied by the anode. Why can't we have instead of the $\ce{Cu}$ cathode, simply the wire connecting to the anode which will supply electrons to fuel the reduction half reaction?
You could certain have a zinc-copper cell in which copper was not the cathode material.  Graphite or silver or whatever could be the electrode material instead.   But once you close the circuit:


Current flows
Cu is deposited as a metal solid on the electrode surface, whatever it is made out of.
Copper metal is, as it always is, conductive.
As a result of steps 2 and 3, there is now a copper metal cathode instead of a cathode made of another material.


So even if you start without a copper cathode you wind up with one.