You need to make sure the scenes you include in a showreel feature you. You may need the occasional shot of another actor for the scene to make sense, or for context, but this is YOUR showreel. A casting director may simply skip through your reel, stopping at random points – and if each time they stop they see another actor, or a prop… you’re missing the opportunity to present yourself to them. Your editor should be able to recut your scenes to focus more on you, while keeping the sense of what’s going on.