While the exact speed of a hyper-drive is still a debate, most fans agree that it'll take you across the galaxy in days at most. Given this, why are the outer-rim worlds still so intensely impoverished backwaters complete with scum and villainy? It would be like claiming that San-Francisco is simply too far away from Washington to govern effectively since it would take ages to reach it by car or train. I mean Greece is not a frontier land to the British by any stretch of the imagination, so why should Endor be to Coruscant?

This problem gets even worse when you consider that the Star Wars universe has instantaneous messaging across any distance.

I am of course aware that the "real reason" its that George Lucas wanted to use backwater-worlds as they'd be cheap enough for filming and then hyper-drive's fast speed was set, so I am looking for an in-universe explanation (presumably from legends as I doubt there is one in canon).