There were many different Rebel troops and pilots available, so why did Leia ask Obi-Wan for help?
Leia chooses to ask Obi-Wan for help because vital Rebel plans must be transported to Aldeeran. Obi-Wan knew Leia’s adoptive father, Bail Organa, who is capable of deciphering the Rebel information.
Considering that Obi-Wan is one of the last remaining Jedi, Leia considers him best suited to complete the difficult, yet paramount task. His prior relationship with the man who can decipher the message also makes Obi-Wan an important choice.
Leia chooses to ask Obi-Wan for help
In Star Wars: Episode IV – A New Hope, Obi-Wan saves Luke from a gang of Tusken Raiders. Known only as a crazy old man, Obi-Wan is actually a powerful Jedi Master who’s been tasked with watching over and protecting Luke.
After the Tusken Raider attack, Luke explains that R2-D2 is on the lookout for an “Obi-Wan Kenobi.” Obi-Wan, no longer pretending that his first name is “Ben,” invites Luke and his droids into a cave for protection.
Obi-Wan taps a button on R2-D2, unveiling part of the projected message. Princess Leia, in hologram form, speaks.
She refers to Kenobi as General, and says that years ago he served her father in the Clone Wars. Leia’s father now begs for Obi-Wan’s help in his struggle against the Empire.
Leia says she regrets that she can’t deliver this message in person, but her ship has fallen under attack. Her mission to bring Obi-Wan to Alderaan has failed. She goes on to explain that she placed information vital to the Rebellion into the memory systems of R2-D2. Her father will know how to retrieve it.
The Princess urges Obi-Wan to safely deliver R2-D2 to her father on Alderaan. As this is her most desperate hour, Leia says, Obi-Wan Kenobi is her only hope.
Obi-Wan and Luke agree to transport the plans
Due to Order 66, the extreme majority of Jedi have been wiped from existence. The remainder live in scattered secrecy throughout the far Outer Rim of the galaxy. For the imperatively important mission of transporting Rebel plans to Aldeeran, Leia needs a Jedi’s assistance.
Obi-Wan and Luke travel to the Mos Eisley Cantina in search of a pilot. While there, Obi-Wan is forced to use his lightsaber in the Cantina when threatened by local thugs.
So that’s the answer. Leia chooses to ask Obi-Wan for help because vital information must be brought to Aldeeran. Obi-Wan knew Leia’s adoptive father, Bail Organa, who can decipher the Rebel message.