Thy operate on a simple concept of trisecting a cam lobe so that, as the device is retracted, the cam unfolds and permits an amazing range for a unit of its size.
Another argument again the service locator pattern is this: If you ask the locator for a service which has dependencies you have to resolve those dependencies yourself. So you need to know about the specific implemntation of this service interface which defeats the purpse. If you work around that, you end up with something that is pretty close to a DI container.