Kurt Vonnegut actually commented on this back in the day (although more just the fictionalization of reality through media, in his case novels). He would often stop his stories to go into the personality, history, dreams, and goals of walk-on characters, like a random waitress in a coffee shop serving one of the main characters.

Just as a reminder to the reader that the person serving you coffee has all those things. They aren't just some unimportant side note building up to a climax of your story: they're a person with their own story too.

I always liked those little sojourns, and the lesson was invaluable.