Dave Meltzer confirmed in the Wrestling Observer Newsletter that the reason why they are bringing in Austin is that they have not sold out MSG.
The announcement of Austin returning did help boost ticket sales and they are expected to sell out. However, as of this writing, there are still some tickets available.
Meltzer noted that WWE feels it is important to sell out MSG because they are trying to keep AEW from running that building.
The Undertaker is advertised for the 9/11 SmackDown Live in MSG. We could see more of Austin in the near future. He has said that he is open to doing more reunion shows if the Raw Reunion becomes a yearly thing. Austin is also in the new ads for Friday Night SmackDown on FOX. Click here to see the new commercial with the new logo.