Probably because his contract with Fox doesn't allow him to speak at political rallies for some reason or other. Makes sense in a way considering his various commentator jobs. However, it appears he can show up and work the crowds.
You can bet your bippy Sean would LOVE to get up on that stage in front of thousands to speak.
But not to worry, everyone knew he was there and the crowd went bonkers.
Leni
That would be overkill.