It seems like quite a personal thing - I don’t use sleeves myself since the only reason I’d have to care about dust or fading would be if I’d bought something as an investment and wanted to preserve its value for later resale. Given that the only reason I buy media is to keep and use it however, I don’t really see the point.
Others do seem to like keeping things pristine though - I guess it brings them a certain sense of satisfaction to have mint copies, and far be it for me to disagree with whatever makes them happy.