Physics and Economics

The physics for large things like galaxies is different than the physics for the tiniest quarks. That much is known and accepted. However, the holy grail for physicists is a unifying theory that would unite both the gigantic and the microscopic. 

Likewise, economics has been divided into the study of the large (Macroeconomics) and the personal (Microeconomics). Yet you never seem to read or hear about any economists working on a unifying theory of economics. This seems odd to me. Like such a theory is not a priority. Makes me wonder if it is because economic decisions are made by people who aren't always rational or because economics isn't really a science?