Well, as for the Jawas picking up scrap that we never see in service in the PT, we never see the scope of how far they travel. They could be going to locations that we never see, so I am ok with that.

Maybe Tatooine is the only place that has the proper environment that supports Jabba's species, so he has to stay on that planet? So I'm ok with that too.

It is hard to explain Luke's view of Tatooine in light of the prequels. However, we don't really learn from any of the films how far the Lars homestead is from any populated area. Luke's view of Tatooine may be very small. Yes he gets to use the landspeeder and the t-16, but maybe he isn't allowed beyond a certain point or 'There'll be hell to pay'.