Suppose you develop a new course, one that has never been taught before anywhere else. I'm not sure if any of the classes I've taught are entirely original, but a couple of them might be.
It occurs to me that my students get course credit for taking my classes, but I don't get course credit for teaching it! Some day it might be nice to, you know, have a Bachelor's degree in game design from all the courses I've taught. But it's never going to happen, because I don't actually get course credit for teaching my courses.
In some ways it shouldn't matter. In theory, if I'm qualified to teach a course, it may as well be on my transcript anyway. In other ways it most certainly matters; if I teach a class at the graduate level when I don't have a graduate degree (yes, this can happen), it would be nice to get some credit hours towards my own graduate degree!