As usually there are a lot of things designer would love to add to their work and cannot. The idea behind Crusader lore is to write down all that cannot be in the mother book. Even if this is a supplement, not a game book itself, it's very interesting and maybe a must-have to ambitious storytellers. The screen? Maybe people don't want to build walls between Storyteller and players. It's useful, howere, as a tables-summary.