I've decided that "steep learning curve" doesn't have to do with mathematical graphs at all. Saying something has a steep learning curve is the same as saying

I've decided that "steep learning curve" doesn't have to do with mathematical graphs at all. Saying something has a steep learning curve is the same as saying there is a barrier to entry. That barrier is knowledge, and a steep path over that barrier indicates a lot of of basic knowledge is necessary to get past the barrier.