Because Arsenal are (or were at the time) the only team with centrebacks who could be bullied by someone going in hard and doing little else. A legless Shearer did the exact same to them, back when he was being back pocketed by decent centrebacks every week elsewhere in the Premiership. "Stick it up the Arse" worked for only one game a year, everyone else pretty much laughs that sort of tactic off with their big, strong, 6-foot centrebacks. Watching Smith trying to out muscle them was like watching a kids training session where the adult coach has the ball and you have a swarm of midgets all buzzing around him trying to get the ball and tripping over themselves in the process.
He had a run of games up front under Big Sam iirc, and was utterly useless, especially alongside Owen (who was also useless prior to Keegan coming in). Might be why it's difficult to remember.