In this potential situation the batting team has a recognized batsman and a tail ender at the crease, the recognized batsman is facing the last ball of the over and the fielding team therefore would prefer that either: he doesn't score any runs, scores 2 runs or scores a boundary so that at the start of the next over the tail ender will be on strike and not the batsman.
Supposing he hits the ball into the outfield but only takes a single run so that he retains the strike, would it be possible for the fielding team to deliberately kick the ball over the rope so that 4 runs are scored and the tail ender will then be on strike?
Clearly the situation would be pretty unsporting!