I've actually came across this key in an apartment building in Berlin once, so they really are still in use. The person living there did complain about it thoug

I've actually came across this key in an apartment building in Berlin once, so they really are still in use. The person living there did complain about it though, as (at least in the evening) you had to collect guests from the main gate and escort them back there when they leave, since using the key was the only way to open it. Understandably this is quite annoying when you're living at the fourth floor.