A well trained Springer does well when left alone. Make sure your dog is in a safe environment, preferably a large crate or pen, while unsupervised. As with most dogs, a smart Springer can think up all sorts of amazing mischief to keep himself busy when you are not at home.
Additionally, in case of an emergency such as a fire or an earthquake, for example, it is important that the owner or rescue crews can locate the animal quickly, without further risking human life to search for the dog. Keeping the dog penned or crated can facilitate its rescue much more effectively. Since it is most likely that the animal will spend much of its time sleeping while its owner is away from home anyway, it just makes good sense to keep it penned or crated for its own protection.