#3 Would have killed the SmackDown Live main event spot
You have to remember that WWE has to do not just one but two shows every week. While Kevin Owens and Stone Cold Steve Austin could have brought the house down with Stunners, it would have ruined SmackDown Live.
SmackDown's plan was to go off the air with Roman Reigns and Kevin Owens standing tall, laying waste to Shane McMahon's big plans. Having them work in concert was the biggest thing on the show, and the ultimate thing that would get fans pumped up.
RAW crossed the 3 million mark in terms of viewership in the United States and SmackDown really needed somewhat of a viewership boost. Would it have been possible without the sight of Shane McMahon's evil plans crumbling all around him?
Because this was already planned for SmackDown Live, I'm guessing that they didn't want overkill with RAW as well!