POI markers are similar to scenery landmarks (e.g. buildings, airports …), which need to be defined explicitly by addon author.
The reason why many addons are without POI marks: I think many authors are just too busy with the modeling, or would rather leave your the fun of discoverying.
While personally I would like to see as many explicit POIs as possible, which can give me clear goal. That’s why I’m working on making supplementary POI marker addons. Welcome to check out my uploads to see if they can be of any help.