Does not exist in Germany either. Most of our regular mail delivery is done by foot or bicycle, except in very sparse rural areas. And our mailboxes have locks

Does not exist in Germany either. Most of our regular mail delivery is done by foot or bicycle, except in very sparse rural areas. And our mailboxes have locks anyway. So it's either the post office or a street mail drop-off box/pillar box. Nobody I know does regularly post letters anyway, it's more in the range of 1-2 letters a year if even that.