Easy to follow why there's so much Tatooine in the movies;
Anakin Skywaler- Raised on Tatooine. Tatooine had to be in Ep1
Again, Anakin went back to save Schmi; Ep2
Also in Ep2, we see Owen and Beru Lars, no doubt a connection between them and the Owen and Beru Lars in Ep4
Ep4-Luke was raised on Tatooine by Owen and Beru Lars. Not having seen any spoilers, I'm guessing Ben put him there, and hence Tatooine had to be in Ep4
Tatooine is not in Ep5, except they mention that they're going there in
Ep 6- a bit silly to put "We're going to save Han at Tatooine" at the end of Ep 5 and then have them save him on Ryloth
Politically, Tatooine isn't all that important, neither by location. People from Tatooine take a big chunk of important pie though.