^^^1) The move doesn't fit the WWE at all. No one would ever let someone use that move for many reasons. It's damn near impossible to set up, considering realism as well (reason why I don't like it very much), the risk factor is high, and when's the last time you saw a finisher executed from the top rope? I mean they somewhat tried it with Kennedy, but they dropped the ball on that now he just does that same finisher on the ground and has a similar name as to Punk's.
2) It would be the EXACT same issue that is being criticized now with the Go To Sleep as his finisher.
3) "The OMG Triple H/Stephanie Backstage Politics Abuse" reason. It would make the Pedigree look weak, thus Triple H, who wants to be da best wrestler in da bizziness with da best finisher, will definitely not allow him to use it at all costs (even though the Pedigree is 3x easier to set up, so imo is stronger).