Kinematics
Hero
It turns abstract numbers into a concrete idea that people can grasp. It provides a word and description that can be used to help shape an idea for a character. Lacking that, it can be very hard for some (some more than others) to actually build a character of their own (in the story sense, rather than the mechanical sense). The background descriptions and names provide a starting point for those who have difficulty with that.That said, why have the background tied to mechanics at all then? If I can play an Acolyte with +1 Wisdom, +2 Dexterity and the Tavern Brawler feat then why even have a sailor with those printed feats and ASIs?