It’s A Small World After All: Partially justified, in that (a) there are generally a limited set of places to land – Landing, Star City, Phílae Interstellar Starport, Stationary Station, etc., and (b) most people who have any sort of regular offworld dealings live there, or maintain offices there, or at least have some kind of representative or path-pointer there, so if you’re visiting on any sort of regular errand, you just land at the big starport and you won’t have much trouble finding them.
Averted for all other purposes, in that most planets are bloody huge, and – except for new colonies and outposts – covered in unspeakably large numbers of cities containing millions to billions of people, and to get anywhere – because no-one puts a starport downtown anywhere except Star City – requires extensive use of long-range on-planet transport. And even thinking about meaningfully conquering or controlling one through force of arms requires absurdly large numbers of troops given their typical population and area, so if you have ambitions of joining the Interstellar League of Tribal Chiefdoms, better hope you brought the armada of self-replicating war machines. You’ll need ’em.