This arrangement needs to be removable for tuning and for maintenance of bearings in attached parts.
Over the course of my career in sports design, the question of screws of rivets comes up. The choice of a rivet is more economical, but unforgiving, the downside is repair or replacement. The companies I have worked for have opted 95% of the time for screws, until a product becomes so mature that not change or replacement of parts is almost guaranteed.