The observation that simple, purely deterministic traffic models possess jamiton solutions indicates that phantom traffic jams are not necessarily caused by individual drivers behaving in a "wrong" way. In fact, they can even occur if all drivers behave by the exact same laws. In the considered traffic models, two key effects work towards the occurrence of phantom traffic jams: first, denser traffic travels slower; and second, it takes a certain "adjustment time" for drivers to react to new traffic conditions. These effects are counter-acted by a certain tendency of the drivers to drive preventively. In light traffic, the good effects dominate. In heavy traffic, the bad effects prevail. Hence, phantom traffic jams are probably an unavoidable feature of traffic flow.