How many people have you seen (or even you yourself) block off an area of your house with blocks or ropes or Krokatopia Hieroglyphics?! Some houses kind of have the concept where when you walk through an entrance the door opens for you and you feel special as an owner but then a friend comes over and it does the same thing for them as well. I believe that the doors that are inside houses should be able to close at the owners request. Once those doors are shut, Only the Owner of the house can enter that portion of the house! Take for example the Wysteria Villa. You have all of those doors that are located on each little section of the house and they are held open 24/7. It would be nice if the owners could feel a little more control when it came to their houses and could open or close doors with the press of a button. I think this feature would be greatly appreciated.
The only use I could kind of see this useful for is if you role-play. Yes I do block one of my rooms that is my storage area and that is because it is so messy looking. But I personally don't think having locked doors is going to be of much use. Other players can't pick up your stuff or move it.