We already have unofficial releases of it
All of which could be mass produced on DVD/BD, marketed, and distributed to thousands/millions more people if the films were in the public domain.
Which version would be in the public domain? If anyone was free to distribute the movies, anyone would be free to edit them. And if anyone was able to edit them, which version would be definitive? How would the millions know the difference between the Despecialized Edition, the Silver Screen Edition, the Revisited Edition, the Special Edition, et al.?
I have enough of a hard time finding good audiobooks of classics on Audible. I have to sift through many crappy releases of an audiobook to find one that is acceptable. How does making Star Wars public domain help people find the originals instead of muddy the retail waters with ambiguously named edits and crappy preservations?