The puppet masters wont allow their puppets Harris/Walz speak on a platform like Rogan because they wont be able to control the narrative. We can already see right through the disaster that is Harrs/Walz when they do speak in very controlled situations. 

Now imagine letting them speak on a platform without teleprompters or their people sitting right next to them to pull the plug if the convo starts going south. We already saw that when Harris was interviewed by Brett Baier.