Science Vs Nature

Today science has grown tremendously that one may think, in future science can explain everything but i say its impossible. As science starts with lot of assumptions then it builds a beautiful thoery arround it and starts proving the theory but it never tries to explain the assumptions because it cannot expalain. So science expalining nature is like space the deeper we go the deeper it becomes.
As an example science explains the origin of universe by bing bang theory but it assumes that if there exists a huge mass then it explodes but how did the mass come?? it doesnt explain that because it cannot. No one has ever seen any sub atomic particles its all assumed as that expalins many emprical results but if the assumtions go wrong in some point of time the scientists have to reform the theory again from the begining.
The main point is why doesnt science dare to talk about god it simply says god doesnt exist so to be at the safe side it always tries to bring scientific theory to all the miracles happen but many times it cannot explain but still doesnt agree god exists