In many places, it's a crime according to the law, but if nothing happens with thieves or reported theft, then in terms of consequences it's not a crime.
I think you're using a different defintion of "crime" than I am (unlawful activity is probably the simplest). "Unenforced" would be probably a better term. e.g. Speeding in a car is a crime in a lot of places, but is often unenforced.