They showcase the combat because action looks better in previews. Your base does get raided occasionally, but most of your time is spent balancing all the tasks a colony needs done and maintaining the fragile mental states of your limited number of colonists (it takes heavy inspiration from Dwarf Fortress in that regard).

You can also adjust the settings of the “storyteller” (the AI that makes events happen to shake up the gameplay) if you want a more peaceful community builder sort of experience.