In older stations, transfer corridors were often thought to be crossed in both directions initially. This started to cause some problems in the 1950's, when the passenger trafic rised and the train frequency was much lower than it is nowadays. This was leading to very crowded trains generating huge waves of passengers. The situation was sometimes so critical that people had to queue in order to leave the platforms. You can see that well in that picture:Are there any useful station plans that can help with navigation when entering stations or changing between lines? The corridors at St Lazare/CdG-Etoile/Bastille/Republique seem to be really tangled and hard to navigate
Why were they built like that?
In order to better control flows, they even installed gates at the entrance to platforms to prevent people from coming in when the train was arriving (those gates were deeply hated by everyone in those days).
I think it's in the same period they decided to generalize one-way corridors as much as possible, so that passengers wouldn't clog the people coming in the opposite direction. Many of those corridors weren't meant to be used this way at first, which explains why they sometimes look a bit like a maze, but signage is usually rather good. As a matter of fact, there could be real shortcuts if you would take some corridors in the opposite way, but you risk a fine if you do that! I'm often tempted though.
I actually remember several corridors getting built occasionally here or there in the metro, it's not that frequent indeed. Minato ku probably knows more about that.