The trouble with any such reliable way of communicating with the divine is that it would, ultimately, deprive us of our dignity as truly independent beings. Once the creator makes himself be known in unambiguous terms that are obvious to everyone, you are no longer a truly independent entity, now are you? Sure, you still have your free will, but how much is that worth in a world where you know, for sure, that the Devil exists? How much choice does that leave you, to decide between good and evil?
Is that why Jesus walked around performing miracles? And also why there's such heavy consequence for making the 'wrong' choice? Also I'm pretty sure most people would choose good, especially when given all the information to make an informed choice.