Why did we spend 3 days(thatz 255 minutes) on mass and volume?

The question is "Why did we spend 3 days(that's 255 minutes) on mass and volume?"
My answer is in the future, maybe you will use it, and when someone asking you, " Is this mass or matter?", You can give that person specific answer, and if you are working on the project, and the topic is " What is mass? What is matter?", you can remind yourself that you already learned that before, So I think that's why we have to spend 3 days for learning mass and matter.