IMTU, I'm sticking to the notion that you need some sort of mass to home in on to get out of jump. (Thanks, C.J. Cherryh!) It helps rationalize a lot of "worlds" that are popping up in WorldGen; no pop or low pop, but a decent port in place - there's nothing that's an inherent draw at all. Except - there's sufficient mass, a star, even a large enough rock, to focus on and come out of jump; maybe some iceballs out there to turn into fuel. So a port develops, just a little waystation in the dark, a place where ships meet. And when they get there, they trade, if they can. It's expensive to jump with nothing to show for it. There won't be enough cargo going around to ship in or out of a place like that, but a handful of Free Traders clustered around a barren rock will be ready to make deals. Some of these places will even be able to develop decent port facilities, in time.
Now, I wouldn't go so far as to say that jumping into the dark is *impossible* - just that you've got either have an absolutely crackerjack navigator spending a huge amount of time scanning the dark trying to find a telltale occlusion that somehow hasn't got on the charts. (maybe roll 15+ per week of nonstop observation, + nav skill, + number of months spent looking - IF the Referee decides there's something to be found there)