Was the intention in 1977-1983 that the Jedi were secretive even before the rise of the Empire and the Jedi Purge? That would explain why Han and Motti don’t believe in The Force, Obi-Wan mentioning that Vader was his pupil and Vader mentioning that Obi-Wan was his master doesn’t lead anyone to realize that Vader is Anakin, and why Luke doesn’t recognize Yoda.
I also find it interesting that Luke seems to hide his meeting with Yoda from the Rebellion in ROTJ.