Space stations are not exactly cheap to make and maintain. Moreover, the biggest population center at pb1 is I Bootis with about 2m people. If I could wager a guess, core systems that have more than one colonized worlds are going to get more stations inside the same system, and the same could work for systems with much higher populations.
Regarding Spaceports, I think that when the expansion hits we are going to have a lot more places to dock and interact with. Remember that each and every orbit station is made as an intermediary between the planet and the rest of the world (essentially providing a check-point for trading, customs, immigration etc), so it would not be weird if we saw the possible docking locations at least double.
