It can be hard to keep track of details as a gamemaster. First, you need to remember the necessary details of the world, including those relevant to the adventure as well as random facts the players might ask, such as the next festival day or the last time the nation went to war. Then you need to remember the pertinent details of the adventure itself: what happened last session, what just happened, what will likely happen, and some rough ideas for the future. Add to this all the stuff that has to be generated spontaneously during the session. The players decide to stop at a tavern for a meal. So you create a pub with an innkeeper, whom they decide to befriend. Suddenly, two names are created and have to be recorded in the off chance the adventurers return to the Lonesome Hog Pub and Grill and decide to see how old Horace the Lame is feeling given the wet weather of late.