The idea behind locking doors is to make things slightly challenging for a casual burglar.
My parents live out in a rural area, and they never lock their doors, house or car. The odds of someone driving to their house and burglarizing it are just too low to worry about it - and if someone were specifically targeting their house, they could just break a window and get in that way.
In denser areas, however, that logic doesn't make sense; it's trivial to case dozens of houses in five minutes just by driving down a street.
Locking doors isn't just to prevent burglars, especially if you live around bars. I don't know how many times a group of aggressive drunk football hooligans has got off the elevator on the wrong floor, then tried to get into my apartment thinking it is theirs or a friends. If my door wasn't locked I'd be confronted with 6-7 violent goofs in my living room @ 3am.
My parents live out in a rural area, and they never lock their doors, house or car. The odds of someone driving to their house and burglarizing it are just too low to worry about it - and if someone were specifically targeting their house, they could just break a window and get in that way.
In denser areas, however, that logic doesn't make sense; it's trivial to case dozens of houses in five minutes just by driving down a street.