Why have all of that gear if you're not prepared to use it. If you shoot sports, you know that one lens doesn't cover every situation you'll encounter during a shoot. That 300mm prime lens is great for capturing the action far away, but terrible when the action moves closer. But it's not so great when the action moves closer. That 70-200mm lens allows you to capture the action closer to your position, but doesn't quite meet your needs for the quickly assembled team photo. Yet it doesn't quite meet your needs for the quickly assembled team photo. Of course you can always change lenses. But why change lenses if you have some old camera DSLR bodies sitting around.
The photographer below, was shooting a professional soccer match recently. You can't completely tell from this photo, but he carried 300mm lens (attached to the monopod), a 50mm lens (on his shoulder), and a 70-200mm lens (not seen in the photo) on another DSLR body.
