One of the interesting features of the Blue Sect is their apperance of equality. People of all classes meet there, and they interact as friends.
Yet, is this really true? Notice how everyone acts when it’s revealed that Ciel is protected by Sirius.
People are crowding around him as if he’s a celebrity – or nobility. He’s being treated as someone special. It’s as if these people see him as someone above them and not an equal. Then you have the four doors shown at the end.
While we’re told that only those with bracelets can go to certain rooms, it seems that these rooms are each marked with a specific star. If this is true, then these rooms are only for those protected by one of the four stars. Therefore, these rooms are exclusive.
Despite what is said, there are still classes. Those protected by the four major stars are the upper class and are treated differently. Other members look up to them, perhaps envy them, and there may be rooms that only they can enter.