It's an unprofessional attitude. Gerrard is the penalty taker and regardless of how far we are ahead in a game or if someone is on a hattrick, he takes the penalty when he's on the pitch.
Roy Keane stopped Diego Forlan from taking a penalty for united years ago when he was trying to break his duck, insisting that the regular taker step up. It is just a simple matter of focus
Actually, Gerrard is NOT the penalty taker per se. Rodgers has given SG the
decision on who takes penalties. So what if he wanted Sturridge to get a hat trick? He was obviously confident that the game was already won and he had no reason to think Sturridge would spoon it. This is a non-issue.