As a producer of how-tos or instructions, your goal is to create instructional content to inspire and help an audience that wants to do or achieve something.
Your customers have voted with their money, and they have your product in front of them. How do you know if your instructions are doing a good or bad job?
Measuring completion success is key to understanding how effective your content is, and this applies to all platforms including WordPress.
As how-to creators, while reach, engagement and views are important economically, it is good to know that our content is being used successfully.