Scientific theories can be rejected by new, reliable evidence. This is because they are simply theories, and although may be true in some instances, are not confirmed to always be true.
Of course, scientific theories can be proven wrong and often times are. However, they are not always unreliable either. Most if not every scientific law we know today started out as a theory, meaning that many of them were extremely reliable. Finally, scientific theories in no way stop questions from being asked. This is why there can be several different theories about a single thing.