system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars ROTJ] Why didn't Palpatine send Vader down to Endor to defend the shield generator?

While the point was to tempt Luke into joining the Dark Side, what better way to do it than make his father murder his friends on the surface? Since Luke's whole reason to come to the Death Star was to redeem his father, wouldn't denying him access to his father be a better push towards becoming a Sith? And I wonder how willing Luke would be to convert his father after he killed/captured Han and Leia. 

It's not like the Death Star was in danger of being damaged while the shield generator was up and I doubt Palpatine ever feared Luke so greatly that he'd ask for Vader's protection out of necessity.
gpt
Palpatine's cruelty, sadism, and ego made it impossible to think in such a way. He wanted the grand display, the showdown between father and son to happen in front of him like a live performance. Palpatine had been trying to replace Vader for years, especially after his apprentice learned about Luke's identity. And in the sith master's mind, the only viable replacement for the disappointing chosen one is the chosen one's child. What better way to get Luke immerse in the dark side than the exact series of events that the Emperor planned out? 

Also let's not forget that many of Palpatine's decisions were guided by his ability to see the future. Unlike the Jedi during the clone wars, who had their future vision clouded by the dark side, Palpatine saw with perfect clarity. It's how so many of his plans succeeded so wildly. And he assumed this pantomime in his throne room would end with Vader's death and Luke standing at his side. And it almost happened until Luke suddenly stopped pummeling his father and instead threw his lightsaber to the side.