Originally posted by Sikboy
I'm going out on a limb here, but I think it was because he was the only one who could act.
-Sik
If you look at the "stars" (no pun) of the show, only Ford and Guiness had any acting experience. The rest were all new talent/unknowns.
Its been said over and over on the documentaries that Lucas is a brilliant writer, but as for a script, he failed. He would write some excellent scenes, but as Carrie Fischer would say on interviews, real people do not talk like that in scenes. Thus why the dialogue, for the most part, seems so wooden.
I think the best example of this is Empire Strikes Back, which Lucas did not direct. You get a much bigger sense of the characters versus, say the original Star Wars.