Really?

This is from a 3-story apartment building I stopped at today:

Can anyone explain why the first floor would be numbered 01, 02...and the second floor 101, 102... and the third floor 201, 202...? Wouldn't you get tired of telling people stuff like, "My apartment is 201, but it's on third floor"?

Of course, perhaps this is a product of a mind best left unexplored.