"Merely corroborative detail, intended to give artistic verisimilitude to an otherwise bald and unconvincing narrative."
An element is included in a work, just because the element makes the story better in some way simply for having it, similar to adding spices and seasonings to food.
These elements don't drive the plot or have a narrative purpose, and aren't genre staples. They can add to characterization or World Building
, but mostly the point of them is that having these elements is so much better than not having these elements.
Now even if these elements have some importance to the story, it's similar to a MacGuffin
in that the form needn't be any of the elements, but it's still better to have them.
Of course these elements can seem overused, especially if some feel the overall story is weak, but with a good story, these elements enrich it just by their inclusion.
A Sister Trope
to Narrative Filigree
See also Tropes In Aggregate
Contrast People Sit on Chairs
(when there isn't even this much of a reason for an element to be a trope).
These animals are so much better than without these animals. Or, depending on the animal, much worse (adds danger and suspense).
Other languages can be better.