I don't know the 'art' of robbing...it's not my skill set, per se. But I would be inclined to think that it wouldn't be very lucrative, especially if you're in a stationary setting, i.e. motel room, where you wait for your victim. Sure, I suppose it would work a couple three times or so, but eventually word will get out that you're setting people up. Throw in an anonymous tip to a cop and...yeah.
And some jokers may not take too kindly to being robbed. Since they already know your info (phone number and location, namely), who's to say they won't come back for revenge?
I dunno. It just seems like too much uphill work to maintain the robber angle, IMO.