The level of math. An Econ/math double major is about the right background for an Econ phd program. (I was a math major in undergrad and didn't feel like a lack

The level of math. An Econ/math double major is about the right background for an Econ phd program. (I was a math major in undergrad and didn't feel like a lack of much exposure to Econ hurt me much in grad school, but it would have given me better perspective on the field.) Many Econ undergrads want a "businessey" degree and don't want to take math beyond calculus, so trying to teach "real" macro (which would require coursework equivalent to differential equations) or "real" micro (similar to but less fussy than real analysis) or even empirical research (statistical tools that build on regression) would be rough going. So we teach "intuition" and watered down versions of the results and punt on justification. Plus the "core" undergrad courses have a large service component --- we need good business students to be able to take intermediate micro, for example, so unilaterally ramping up the required smath wouldn't be feasible even if some of the students wanted it. tl;dr phd programs can spend a lot of time teaching students how to use and extend mathematical tools and can cherry pick students with the right backgrounds. Undergraduate programs have a big service component, have to assume a range of mathematical preparation, and have to actually teach "economics" in their core courses -- game theory needs to teach game theory, not how to be a game theorist.