They added it so the people would read it gryphus. And they would feel the spanking they would get if they break the rules instead.
This. You have to interact with it rather than you join the server, disappear for x seconds and you wouldn't have noticed the rules.
Not only that but it has benefits internally, it's flexible (easy to edit -- reads from a file, reads as formatted), it's cleaner code in the source (simpler -- multiple undertermined amount of textdraws have to be created to have a decent amount of text), oh and the text draw was possibly one of the causes of text draw bugs.