Many of our course revisions happen without much planning. A new idea comes down the pike, an interesting technology option becomes available, a colleague shares a strategy that effectively deals with an issue, and we just use it! So, the course evolves and changes but not all that systematically. As a result, most of the change happens at the margins. That's not bad, but it does not result in transformational change. It's not change that heads the course in a whole new direction. That much change makes most faculty nervous. It requires considerable work and often entails using teaching practices outside their current comfort zone.
