In graphics programming for creative applications you put words to actions.
You pass an instruction to the computer to draw a shape in a certain place and colour it a certain way. Obviously there is a whole lot more complexity to this but the crux have essentially not changed since this:
And that is because it is how programming works as a whole. You pass instructions in and in return the computer performs an action.
As an artist however - this is not how you perform an action.
Take drawing a line; you have an idea of where you'd like to put it, how hard to press, the materials involved - and along the way through drawing it you may decide to go completely the other direction, perhaps acting on impulse and perhaps acting out of a feedback loop with the material. A kind of emergent rendering.
This is an immediate response to you creation, vital for the creation of new ideas.
When you take that immediacy away and when you simulate the incredible nuances of working physically you take away a lot of creative possibility.
Computers have incredible potential to be a new responsive, interactive creative medium - it will only be when we understand the differences between what can be written as an instruction and what cannot be, mediating between or joining physical and digital, that we will move on from turtle graphics.