I think all of us want an event as well as Tesla, why would you miss out on a huge marketing opportunity. They just are not ready to be able to deliver cars in any volume, this is the only thing that makes sense as to why they are not doing a reveal and delivery event. I think the 29th is being done so they can say they delivered cars as promised. Personally I can wait to see the real car, but cannot stand all the speculation that is going to continue until the above happens.
At some point Tesla has to decide the Model-X is ready for production (not necessarily "finished") and begin shipping it. In trying to step into Elon's shoes for a moment, I would think that while they do ship the first Model-X in a couple of weeks, they are far from reaching the finish line. I'm sure they have a lot of issues that still need to be worked out, along with new ones they find along the way (probably mainly with the production line).
Therefore, there is a lot of work still ahead and having a celebratory event may not feel right at this time. Of course, from an end-user perspective, it's seems like a big deal and it feels like we should be celebrating.