Brainstorm a list of WIIFM (what’s in it for me?) from a student perspective.
If you can’t think of more than “because you should know it,” then you need to talk to your students and get a better sense of where they are in their learning and where they are going.
If you know your students well but you still have a hard time determining the relevance of a particular learning outcome, perhaps you should consider removing this content from your course.
“What’s That?” flickr photo by Andy Morffew https://flickr.com/photos/andymorffew/16273602209 shared under a Creative Commons (BY) license