Star Wars: The Last Jedi director Rian Johnson has offered an explanation for why it was only Yoda who dispelled some wisdom on Luke Skywalker and not Obi-Wan Kenobi.
Throughout the original trilogy, Obi-Wan Kenobi is by Luke’s side, guiding him along his first steps into a larger world.
Because of Luke and Obi-Wan’s relationship, many fans had hoped Kenobi would return in The Last Jedi as well, but he made no cameo.
By nature of being a puppet Frank Oz could control, Yoda was simply easier to bring back for the purposes of The Last Jedi.