PhDs often make the worst possible developers. People with PhDs (especially in Mathematics) are often lacking the most critical characteristic of a good developer; they don't know why they do things. Being good at math requires being able to solve problems whose solutions often do not have any practical uses or whose practical uses may not be clear. This is very different from how software problems should be approached. Software development is more about finding the right problems than it is about solving problems; to find the right problems, you need to understand the 'why' in as much detail as possible. Every line of code should be easily justified by how it brings the system closer to achieve its purpose. The PhD diploma itself doesn't have much practical use in financial terms; it's not a good investment to get a PhD for purely practical reasons. Detatchment from practicality is the worst attribute someone can have as a developer.