I appreciate Loren's efforts to tackle difficult subjects. The answer I use most frequently is that people have a variety of different views about the supernatural that are not generally reconcilable.
Science is an effort to understand how objects in nature function and interact with one another.
If supernatural causation were included in science, it would be difficult for scientists with varying views of the supernatural to collaborate. Scientists therefore strive to limit the causation models they will entertain to those that can be established by examination of physical data. From a Christian point of view there is something unnatural about this, admittedly. Perhaps the division of knowledge into different categories is a consequence of the fall, or perhaps it's simply a consequence of the finiteness of man. I'm very curious how this can be done.