Why do we need logic? You can become the president of one of the most powerful countries of the world without any knowledge of it. But no one wants to see a big balloon of themselves wearing diapers flying in the sky; neither do machines (probably). Thus, we need to learn logic and teach it to machines to save us from embarrassment.
Digital logic teaches the latter part. How humans make machines that can understand basic logic, how we can do it too are the teachings of the course. I learned how to build a machine that can make decisions based on small basic decisions.