Asking someone about their day just a way to check in with your partner or spouse or friend. It can be an invitation to vent about work, show interest in a project they're working on, or offer them some adult conversation if they have been with children all day.
Recounting every detail isn't necessary. I try to stick to funny or notable moments. It's more a desire for connection than a desire for a precise accounting and i'm glad to skip it if there's something more interesting to talk about.