There is no good to reason to run copper plugs in N/A non-racing apps. Platinum and Iridium plugs are found in OE apps that push 500+ HP and this does not significantly reduce power or economy. It's just silly unless you're flogging your car mercilessly for hours at a time in a controlled off-road environment (or you're racing on the street which is very stupid). For example, copper plugs do have some merit if you're runing track days at wot for 30 minute sessions. This sort of sustained WOT severe duty use in N/A cars can cause welds on iridium or platinum pucks to fail, causing them to drop into the combustion chamber. The same problem can plague forced induction cars with marginal tune in street environments. This can lead to cylinder scoring. Street cars with bad tuning (too lean or too much advance) can drop electrodes or pucks into the cylinder but it's more prevalent when driven illegally (risking the general public). In my opinion, the proper fix is not copper plugs. Loss of license or proper tuning would eliminate the issue.
The copper plug fad for N/A street apps was spawned from ill-advised folks who believe that racing or forced induction tricks are always a good idea on pedestrian street cars. Many of the same folks are running non-approved racing lubes in their cars which can lead to premature wearout or failure.