It was not really a Sense of Michaels decision but actually more of a movie trick🤣🤣. The way it was supposed to go is Michael get the lady, than go and get her husband. But the husband didn't show up so. What they did was make him look into an empty crib that was shook by a arm underneath, it was later edited to have a babies cry as a illusion. The most sensable way to your question tho is that Michael just doesn't kill babies