It's funny, I used to see canon fodder characters as just wallpaper—names to fill out a roster so the main pairing didn't talk to themselves. But lately I've been writing a 'Star Wars' fic focused on, like, a random mechanic on the Death Star, and it's completely changed my mind. You get to build this whole inner life the original material only hinted at. They're these blank canvases where you can explore the everyday consequences of the big epic events without the burden of following a preset character arc.
It's surprisingly freeing. The stakes feel different, lower but more personal, which can be a nice break from trying to nail the voices of the main heroes and villains. Sometimes the story that happens off in the corner of the galaxy is more interesting than the one center stage.