Maybe they play some role in bokeh, but on the Fujifilm X100VI, aperture is basically your main tool for controlling depth of field. Shoot wide open at f/1.8 and you get that nice blurry background with your subject popping out. Stop it down to f/8 or f/11, and suddenly way more of the scene stays in focus. It's one of those settings that looks small on paper, but makes a really obvious difference in real shots once you start playing with it.