I've seen this arrangement countless times in cities:
First key for the gate on the road to get into the yard.
Second key for the gate in the yard to the stairs and elevator.
Third and possibly fourth key for the door to the apartment.
That's pretty normal. I've seen at least once another key for a door between stairs/elevator and the home door. That's because of many burglars in the very first months after the building was built.
That said, I agree with you that living in a place where you only have one key and nothing happens if you forget to lock the door is much better.
First key for the gate on the road to get into the yard.
Second key for the gate in the yard to the stairs and elevator.
Third and possibly fourth key for the door to the apartment.
That's pretty normal. I've seen at least once another key for a door between stairs/elevator and the home door. That's because of many burglars in the very first months after the building was built.
That said, I agree with you that living in a place where you only have one key and nothing happens if you forget to lock the door is much better.