Chessie RG have never really managed to get it right with the night sessions- (even though they only schedule one match)it's not helped by the fact Paris doesn't really have the same weather. It might be warm in the day, but it can be really cold at night.
It is a real waste of a court to have it sitting waiting for a night session, just for the sake of having one.
The other thing of course, is they favour men's matches as the 'big' event . Not all the players are happy to keep being the one doing it (Carlos wasn't the other year). RG are reluctant to schedule Iga to beat someone in a double bagel, after people have forked out for 'night session' tickets .