All of the Following Are Good Reasons for an Applied $4 \times 4$

Short Answer

All of the following are good reasons for an applied econometrician to learn some econometric theory, with the exception of a. turning your statistical software from a "black box" into a flexible toolkit from which you are able to select the right tool for a given job.
b. understanding econometric theory lets you appreciate why these tools work and what assumptions are required for each tool to work properly.
c. learning how to invert a $4 \times 4$ matrix by hand.
d. helping you recognize when a tool will not work well in an application and when it is time for you to look for a different econometric approach.