the teacher was forcing us to do drawings by looking at an object and not looking at our paper at all. I don't really know what that helps with but whatever I guess.
Forgive me if I butcher the explanation but I, too, went through art school and there's a good reason for this.
When you are drawing an object, there's two different 'images' of it in your head. If you're looking at the object, you can see what it looks like. When you aren't looking at the object, you are remembering what the object looks like. The thing is that we're complex, thinking creatures who instead of remembering details in perfect detail, we instead reinterpret images that we remember.
The best way to do this is to pull up a photograph of an apple. First, try drawing the apple from memory, then draw the apple using the photograph as a reference. The two drawings will have some subtle differences and some not-so-subtle differences.
This thing comes up a bunch in spriting because the biggest goal with spriting is trying to represent a real-world object with a limited canvas, a limited amount of colors and usually a bare minimum of details. It takes a pretty talented person to be able to sprite a complex object without a reference.
