Depends on your area of focus. Schools tend to be much more focused on the academic / math than practical application development. CS isn't as critical until

Depends on your area of focus. Schools tend to be much more focused on the academic / math than practical application development. CS isn't as critical until you have to worry about efficiency, scale, or creating radically novel solutions. At which people you naturally will pick up more CS as you try to solve these problems. Building something and building something that can scale are almost 2 completely different tasks. Asking questions like how much disk space will this take? How long will it take to perform a lookup? How do these factors change as the data grow? Another area where CS becomes more important is when you want to come up with new abstractions. To do what others have already done you don't need much CS knowledge because others have created libraries for you and have already established the design patterns. But CS becomes more important when you want to invent new paradigms and algorithms.