Why are functions useful?

Functions are essential in programming because they enable better organization and reuse of code. By encapsulating code into reusable blocks, functions allow developers to write code once and call it multiple times throughout the program, which enhances efficiency and reduces redundancy. This modularity not only makes the code easier to read and maintain but also helps in isolating specific functionality, making debugging simpler. The structure provided by functions allows programmers to focus on high-level design and logic without getting bogged down in the details of implementation every time the functionality is needed.

In contrast, increasing repetition in code leads to a cluttered codebase, while limiting the ability to track program flow creates confusion, making it harder for developers to follow the logic of the program. Additionally, reducing the need for documentation would actually be counterproductive, as good documentation is crucial for understanding, maintaining, and using the code effectively. Thus, the utility of functions lies primarily in their role in enhancing organization and promoting code reuse.