Why do some people believe..... that you can't be a scientist and still believe in God ?

I don't see the two as unreconcilable, much of the methodology and philosophy that became science comes from gnostics and alchimists who believed that all science brings you closer to god because by understanding his creation you understand god a bit more. I'm not saying that this is what I think just that its not completely impossible to believe and be a scientist. lets say, as a mental exercise, we were to take these two propositions as the truth: 1:god exists 2:he created the world. then all our observations would be interpreted in that context. what seems more of an impossible feat is to be a scientist and have a very specific idea of god. certainly there are contradictions between scientific findings and the bible and obviously the logical solution would be that the scientific observation is reliable, god still exists but the bible is wrong. in that way, being a christian who thinks the bible cannot be wrong is incompatible with science, and probably also prevents someone from actually finding god, if there is such a thing because if god exists then science IS the discovery of god.