Okay, so you know those gates that guard "gated communities" like apartment complexes and condos? I have an opinion about those gates.
Let's say you are going to rob a house.* The gates are not a deterrent. All you would have to do is wait in your moving van until some sucker comes along to enter the code and let you in. Imagine, however, how stressful it would be to have to wait for someone to enter a code to let you out. Configuring the gates this way would also be better for emergencies. Usually emergency responders have to manually pull the gates open, wasting precious seconds or even minutes. If the gates opened without a code on the way in, there would be no delay in treatment.
*Note to current and future employers: This is a hypothetical situation. I have no intention of committing grand larceny. I may consider petty larceny if I can't afford to buy food, but really employer, whose fault is that?