Yoda was on Dagobah for a specific reason. To learn how to interact with the people alive in the universe after he had died, like old Ben did. How to enter directly into the force, like Ben did when Vader "struck him down" in the light saber battle on the Death Star. Ben didn't get killed by Vader's light saber, he simply vanished just before the killing blow.
Ben's teacher was one of the first Jedi to learn how to do this (forget his name) and was actually talking to Yoda from beyond and Yoda went to Dagobah to learn the process. And to kind of hide out.
Dagobah is unique among planets in the Star Wars universe as the planet has become infused with the Living Force. A dark Jedi master was killed there a long time ago. That dark Jedi's energy fused with the planet and tainted it. Thus the reason for why the Cave of Evil exists (Where Luke Skywalker faced himself if you remember).
Few things survive there except for the native species. Expeditions there in the past always met in terrible failure. Yoda made his home near the Cave of Evil. The dark nature of the Dark Side and the power of the Cave of Evil was effective in masking Yoda's presence from the rest of the galaxy, which made it a perfect hiding place for the most powerful Light Side Jedi alive. And Dagobah itself due to it's nature naturally hides itself as well. Dagobah has been discovered, lost and rediscovered many times, despite attempts to log it's location for posterity. Information about the planet always seems to get lost.
The nature of the planet and it's origins of how it was infused with The Force also made it a good place to learn how to become One with the Force, as old Ben did right in front of Vader- "If you strike me down I will become more powerful than you could ever imagine" if you remember his last words to Vader. And powerful indeed he became. Yoda himself became one with The Force in 4ABY, around the time of "Return of the Jedi". Yoda died the same year (became One with the Force actually, he simply faded away right in front of Luke) that Han Solo was finally freed from his carbonite prison. The Force was brought back into balance the same year (When Vader threw the Emperor to his death on the second Death Star).
Dagobah is very important and sacred place to the Jedi. Luke Skywalker as Jedi Master of the Order would sometimes send young Jedi's there to meditate. But those are other stories not yet told in the movies.
TGD wrote:So why not put Leia on Dagobah (or any other of the outer rim planets) like they did with Luke?
Dagobah is very dangerous, not a good place for Leia to go.
Luke had actual family on Tatooine and Leia was adopted and raised on Alderaan by Bail Organa and raised as one of his own children. I don't think she was ever told about her real parents or family. For her own safety.
It was decided that the two siblings should grow up separate (so they both couldn't be taken at once if ever found out) and with loving, caring families, as to be what was best for them. It all worked out pretty well in the end I guess. Except Alderaan was eventually destroyed by the First Death Star, so that wasn't a very good outcome.....
