On flat ground the logic is simple. There is a ground floor that anybody can walk up to, and there are upper floors that they cannot, and people secure accordingly. Build the same house on a one-in-four slope and that reasoning falls apart: the level that is buried against the hillside at the back is fully exposed at the front, the garage sits beneath the living area with its own side door, and what the owner thinks of as the first floor opens directly onto a terrace at street level from above.
The practical consequence is a door that nobody has really considered. It is usually on the lowest level, it usually leads into a garage, workshop or store rather than into the house proper, and it is usually fitted with whatever the builder had spare. It is also, on a slope like this one, frequently the most approachable point on the entire property — reachable from the road below without passing the gate everybody thinks of as the entrance, which is why an honest security lock upgrades assessment here nearly always starts at the bottom of the plot rather than at the top.
Once that door leads into a space connected internally to the rest of the house, it stops being a store-room door and becomes a front door with the wrong hardware on it. That is why so much lock installation work here happens on entrances the owner initially describes as unimportant, and why we ask to walk the whole property rather than only the level we were called to.