We aren't to pray only if we have a scientific theory which
explains how our prayers should be answered. But in the vast majority
of cases, God works through natural processes & in accord with the laws
we have discovered which govern those processes. (Which is simply
another way of saying, "Scientific description of the world has been
pretty successful.") I think it is helpful to be able able to see how
God can work within that framework & still have the freedom to respond
to petitions. Otherwise one simply has to make a sacrifice of the
intellect & pretend that God performs miracles with a frequency which
would make the whole scientific enterprise problematic.
Note also that the regularity of the world which is a
consequence of God's operational within a framework of contingent
rationality is grace, for it gives us the gift of understanding the
world. A universe which operated by continual miracle would be a
nightmare - we would have no idea what was going on.