#3 Creates a new reality
The best thing about WWE's announcement of a Boneyard match between AJ Styles and The Undertaker is the fact that no one knows what it is about. Not only does this allow the company to do whatever they want during this match, but it also creates a new reality that the company can utilize in the process.
Think about it -- WWE has done an awesome job of creating a new reality with The Fiend this past year and now know what it takes to make a particular world special. So what is to stop the company from taking what they learned from Wyatt's newest creation and translating that into some kind of paranormal adventure?
Where WWE ultimately decides to go with this remains to be seen and will probably depend on what they want to accomplish, but the possibilities are truly endless. Beyond that, it is a beautiful distraction from the empty arena that some of the other matches will take place in.