One reason to think a bit before drifting off the centerline is other aircraft, an aircraft going around should be on the dead side of the runway and looking for you on the centerline, if you drift onto the dead side and he does not have you in sight there could be a loud bang. Also, if you are staying in the circuit it can screw the circuit up by giving you a short crosswind - I am not saying going off centerline for the reasons given is neccessarily a bad thing, just that there are other considerations in doing so.
