Why did tuxedo mask leave the sailor scouts?

Answer 1

Well, technically, he was never an official Sailor Scout. He did stop fighting with them a few times, though, and this is why:

The first time he stopped helping them, it was during the first season and because he was captured and brain-washed by Queen Beryl.

The second time it happened, it was because he had amnesia. In the original version of the story, he and the Sailor scouts had all died in the fight against Beryl and were resurrected by the power of the Imperium Silver Crystal. In both the original and the English versions of the story, though, he and the other Sailor scouts all lost their memories after the fight. (It should be noted, though, that Darien's soul returned to help the Sailor Scouts even when he had amnesia. This was in the form on the Moonlight Knight, who was an astral projection of Darien's.)

The third time it happened, it was because Darien had temporarily broken up with Serena. He had been having nightmares that staying with him would get her killed, and he believed them for a little while. It should be noted that, at least in the manga, Darien actually DID have some psychic powers. It turned out that the dreams were being caused by something else, though, so he got back together with Serena after finding out they weren't based on any actual reality.

In the Stars season, it was because he had travelled to America to go to medical school. Not only did this hurt Usagi a lot, he was killed by Galaxia while he was there. Again, though, the power of Sailor Moon's crystal eventually allowed him to return to life.

There might have been some other times when Tuxedo Mask stopped helping the scouts, but I've forgotten when they were.