Editor at Lookout Games
The rules for setting up the special buildings are pretty straightforward: select 6 randomly, leave them face-down. Now, to this point, all I've played are 2- and 3-player games. In a 3-player game, for instance, only four special buildings will come out during the course of the game. Obviously if you're in the Marketplace you can influence the final choice, so that fifth card will be seen. But why do you need six cards in a 3-player game?
You don't. They just didn't want to blow up the rules with exceptions for 1-3 player games.