Why did Obi-Wan Kenobi wait so long to train Luke Skywalker in Star Wars? George Lucas' original film from 1977 launched the space opera that has continued to thrive more than four decades later. While the franchise has significantly expanded, the original trilogy is still an audience favorite.
Lucasfilm is about to explore more of what the Jedi Master was up to leading to his appearance in the original Star Wars film through the Obi-Wan Kenobi limited series which will be filling narrative gaps on the character's overall story. Long before this new project was announced, however, snippets of his life in Tatooine has been briefly revealed; still, the question about why he didn't simply start Luke's Jedi training earlier remains to be unanswered.
Based on what's seen on Star Wars Rebels season 2, Obi-Wan remained committed to keeping an eye on Luke in Tatooine. In fact, it was only when Maul subtly hinted that he knew of the existence of the young Skywalker that he got a noticeable reaction from the Jedi Master. Between this and the Lars' knowledge of Luke's lineage, it would've been fairly easy for Obi-Wan to slowly train Luke earlier.
Granted that Owen supposedly didn't want his nephew near his secret guardian, it doesn't seem like enough reason for Obi-Wan to keep his distance if he truly felt the need to train Luke. Given this, he may not have been keen on imparting Jedi wisdom to Luke early on for a couple of reasons. For starters, this could prematurely open up the can of worms regarding what happened to his father and mother. Even if Obi-Wan were to be totally honest about what happened, it's not outside of the possibility that Luke would be adamant about seeking answers himself, perhaps even reaching out to Darth Vader. As seen in the original Star Wars film, Obi-Wan was careful about the details he was sharing with Luke with regard to Anakin, skipping that his father fell into the dark side and became Vader.
In conjunction with this, training a much younger Luke could've also revealed their secret whereabouts. Both Obi-Wan and Jedi Grandmaster Yoda had been adamant about keeping a low profile to ensure their safety. Openly training Luke, who's also strong with the Force like his father, could tip off the Empire, not just about their location, but also the existence of a Skywalker heir. This was also the same reasoning behind the decision to separate Luke and Leia following their birth. Keeping two individuals who have a powerful connection to the Force increases the chances of them being detected by Darth Vader, or worse, Emperor Palpatine.
Overall, this proved to be an effective strategy since the Skywalker twins' existence was never revealed until they were directly roped into the conflict between the Empire and the Rebellion. In any case, given Luke's lineage, it didn't take long for him to grasp the idea of being a Jedi — at least the basics of it.
The Obi-Wan Kenobi live-action Star Wars series can provide a clear explanation to this question and so much more as it tackles the titular character's life 10 years after Star Wars: Episode III - Revenge of the Sith. Perhaps his currently-unknown reunion with Darth Vader during this time which will be shown on the Disney+ series motivated this decision. Whether or not this is the case, the idea that the friends-turned-foes will once again face each other, this time on the small screen, is exciting for many.
