I've seen folders worn out with oil. I don't think oil helps a knife with nicely fitted properly hardened parts. And it doesn't help a knife that's prone to galling and wear. Those things are built into the knife. Oil only masks it for a while.
Furthermore, oil always attracts dirt, with increases wear. Oily dirt is still abrasive. Prophylactically oiling a well made knife ends up causing problems rather than preventing them.
Smoothly mating surfaces and decent hardening make oil pretty much unnecessary.