Re: Luke not knowing what Yoda looks like: If OT was the only reference point, I guess this would be easier to explain away as the culture of communication is just way different from ours. It's a mixture of modern and ancient stuff. I don't remember any photographs (although cameras clearly exist), paintings or other depictions of likenesses in the OT.. Were there any? Even writing is almost non-existing. The recent SW Rebels propaganda posters and the presence of graffiti seem a bit off because of this.

If you add PT and EU to the mix, I'm pretty sure it is impossible to explain all the stuff mentioned in this thread with sound logic so I'm not going to even try. It's a mess. If I think about OT only, I can buy the notion that, due to the aforementioned difference in communication and the fact that the Jedi are a religious (mystical, esoteric) thing, finding out the truth about these things is very hard. So hard that even the chosen one had to go to great personal lenghts to find out some facts about things that seem to be shrouded in secrecy, legends and misinformation.

As for people (including all kinds of creatures) in general, it's a vast galaxy where most cultures seem rather primitive (due to the Empire eating up the developed ones?), so perhaps people just don't know or care.