The last ten years or so has seen a change of emphasis within the discipline of Economics, with a shift from high mathematical theory to more applied, empirical work. The evidence for such a change is diffuclt to quantify and often anecdotal, but these anecdotes now pervade the profession of Economics and relate to individuals with theoretical specialisms finding it increasing difficult to find jobs, certain top journals focusing increasingly on empirical topics, UK funding bodies increasingly prefering empirical work and so on. The link below comments on this change of emphasis and suggests possible explanations.
I suspect there are a variety of reasons for the decline of high theory, one being the growing exasperation with its pointlessness, the other being the increased availability of data (mentioned in a comment on the article). In particular there has been a significant increase in the availability of data on the web. Even 10 years ago you'd have to pay for, or subscribe to, many datasets. Now most data by institutions such as the World Bank are freely available online. As Environmental Economists, we also have free online access to a large number of different sources of pollution data (CDIAC, WRI etc). Applied Economists have never had it so good :-)