There is no evidence that any god or gods exist.

As time goes on and we learn more about the universe, we have consistently learned that a god hypothesis is unnecessary to explain the world as we see it.

The god hypothesis is intrinsically untestable.

There is no reason to believe in something without any evidence to suggests that it is real.

The god stories offered by religions tend to be riddled with inconsistencies and claims that flat-out contradict our observations of the real world; when viewed dispassionately, they are indistinguishable from mythology.

Mainly because they’re scientists. See, the pursuit of science requires logic, rationality and reason. Three things which are anathema to religion.

So it’s no wonder that a great many scientists end up as non believers, since it is very hard to maintain faith when everything you know about reality points against it.