A quickie: Lufthansa's very interesting A340-600

Last year on a trip from New York to Frankfurt I flew the Lufthansa A340-600 for the first time. The planes were pretty standard except for one feature only available on the LH A346. Instead of having a few bathrooms next to the galley in between cabins, on these particular planes they have a staircase. To get to the bathroom you have to go all the way downstairs. On the bright side this allows them to fit more restrooms than usual. It is like a normal bathroom will like five stalls. The bathrooms were fairly pleasant. What is the purpose of having a staircase down to the bathrooms? I found a video to show you so you can see what I'm talking about.