The “official” reason would be that Science makes an a priori assumption that there is no god, and everything must be explained without reference to such. An a priori, or prior assumption, is one that is made without research or evidence. As Wikipedia puts it, you don’t even need to get out of bed to arrive at it.

A more realistic explanation is that most scientists, like most people, want nothing to do with God. Anything that points to the Earth being in a favoured position in the Universe also points to a Creator. Therefore, given two possible explanations of an observation, the one chosen and promoted will always be the one that points away from God.