They worked because there was no real internet to speak of. Yes, you could put that text file on a floppy or print them out, but outside of your friends, there was no real simple way to spread that information. BBS distribution was also so small it would not have been a thing.

Additionally, most(?) of the code wheels had multiple discs stacked together. i.e. it wouldn't be a two-dimensional lookup table, but three- or four-. IMO it would be more likely for someone to write a simple software utility to emulate it, but it would probably be simpler than that to just remove the check from the game :).