Put simply, causal determinism expresses the belief that every effect has a cause, and therefore science, pursued diligently enough, will explain all natural phenomena and thus produce a TOE (Theory of Everything).
This idea goes hand in hand with materialism. Scientists and skeptics may implicitly favour causal determinism because it does not allow for any supernatural explanations of reality.
As Pierre-Simon Laplace noted around 1814, such a theory would also (in theory) grant a sufficiently powerful being the ability to determine any future state of the universe, thus making the future as readily accessible as the past (at least from that powerful being's frame of reference).
See also: Determinism