Here almost everyone's locked themselves out of their place at least once, LOL. Many people keep the number of a cheap locksmith/key service in their wallet for emergencies if they don't have anyone nearby they're happy to give a key to.

(Worst is if the door falls shut on you with the key in the lock from the inside, because then it can't be opened from the outside even with a key, and you do need a locksmith. Ask me how I know ... *g*)