Ever heard of Booleans? Most objects are simply a combination of the 4 primitives. These exercises will help you improve your understanding of how the 4 primitives interact with each other. I'll admit, this is probably more complex than it needs to be, but the stronger your knowledge of these fundamentals, the more quickly you will be able to sketch complex shapes. If anything, these are a set of tools to help solve complex problems down the line with the simple concepts covered here.