To summarize, good packaging is important because it enables changes to code to happen faster with less risk (it is easy to grasp what to change and where due to the clear separation of concerns within the modules). This also leads to fewer bugs in production.
Good packaging also helps the non-technical aspects of engineering: there is a clear quanta of ownership for teams, and so there are fewer conflicts/communication and more of a sense of ownership.
In the next chapter, we will begin to look at design patterns. These are blueprints for solutions to various well-known scenarios that we encounter in software engineering.