Not only do docking rings look nicer compared to the red crosses, it also provides that not everyone can just enter the planet. Making an open zone accessible for every party would require an increased amount of defense installations around the planet in order to prevent that from happening. Docking rings seem to fulfill that purpose perfectly. Ontop of that, I don't think it takes as much effort to actually build those, considering we're more than 1000 years in the future. About the missing lore regarding it, well, it wouldn't work for already mentioned places such as Malta or Crete if Ageira was the only faction able to produce the parts. There should be a consensus about it at some point that makes it approachable for other factions more easily than when talking about trade lane components etc. Obviously, building docking rings also probably costs a lot of materials and thus makes it so not every small pirate group can build them.
