To echo what Jonathan said, a full reunion would have brought upon astronomical pressure. Though it might seem silly to us, because Page/Plant was a big deal anyway, having JPJ would have brought the big time back.
I think if John Paul had been invited, there would have been a mass outcry that Michael Lee was no Bonzo. I thought Michael Lee did a really good job. I think Page and Plant should have given John Paul a "heads up" about their upcoming tour, it seems that John Paul was ambushed by the press. It was great to see all three of them at the Kennedy Center Honors, plus Jason Bonham. After the Kennedy Center, RP, Jimmy and John Paul visited The David Letterman Show. Letterman was seated next to Jimmy at the Kennedy Awards. 🎶💙🎶