Steel and aluminum cases cannot be reloaded, but you used to be able to find boxes of Russian steel cased 9mm for as cheap as $5-6. Reloading costs around $0.07 a round, last time I checked, so at $0.10 it made a strong argument for saving time.
After seeing True Velocity's 6.8 mm cartridge, I'm convinced that polymer is the future, but that doesn't mean WWII cartridge technology will die. Russia uses steel cased ammo because they don't have large domestic copper reserves. Russia basically invented the steel case, and they had perfected it by WWII. Germany also lacked copper, but they were late to develop steel cases, and the early 98k rifles were overpressurizing from the steel jacketed bullets and the MG34s were tearing case heads off. I think some other national armories still use steel.
The biggest issue with steel cases is actually the bimetal jackets. If they often barely use any copper in the top coat and it basically just lubes to barrel a little bit. Thick bimetal jackets work great. The big reason for most people not to use steel 9mm is the rules at indoor ranges. They say something about steel 9mm chewing up the rubber backstops.