Nowadays, even if you're going to the corner store for a six pack, you'll lock up your house before you leave. Generally, you do the same at night, before going to bed. Security is a way of life, with the world as it is now. What happens if you go to the store, leaving the house unlocked because somebody else is in there, and neglect to take your key? The last person in the house is responsible for locking up, before leaving. If you get home, discover the house locked, and realise then that you have no key to get inside, what do you do? Do you call the police, and demand that they send an officer over, to help you break in?
Do you call the home owners association, or maybe the landlord, and request key service?
If the home owners association, or the landlord, can't be reached, do you complain if they can't provide a 24 hour emergency number, to service you when you are locked out?