I have locks like this in my home. I got a new front door and locks when i moved in [1], and the locksmith offered me the option of these (it's called a thumbturn lock here), which of course i took, because it means you don't need a key to hand to open to door to let someone in, or to escape a fire.

[1] because the previous owner's tenants had broken the door down at some point, and he had replaced it with an internal door, in which for some reason he had installed the lock upside-down

I've not seen them in Germany for example, but the cylinders were standard, so it's an easy swap (you can keep the old lock and swap it back if you leave). Keeps you from being locked out, for sure.