It all depends, if its an existing cable that runs into an attic or basement or whatever that COULD be used in the future for some unforseen thing, then I will leave the conductors in the box and cap both ends, that is providing its NOT obsolete wiring such as K&T or romex with NO ground.... If its a useless cable ( goes nowhere, has no ground etc.) then I will cut it off short so it cant be used.
