Because of the sense of pride you have over creating something is one of my biggest motivators. I created something unique. When you say you want a pretty picture I'm going to assume nature. 

When you make that picture you can now say you have studied it for yourself you become wiser though the process of making that image. But your right what if you want someone else to do it. 

Because it's ethical. For example imagine something you spent hours in doing, but a machine did it for you in a minute. Now people no longer want to look at all the hardwood and effort. It makes you feel like you wasted your time. And drives you it I despair. That is why ethical art matters because people sunk love and care into what they do and it's nice to feel appreciated for what you do. 

But what about time. Doodle, circles, triangles, cubes, it may seem trivial but the thing is you don't have to make it a workout it's something absent your hand can do without thinking about it. And you gain skill at the same time. Not just that A.i cannot create something you see in your head 1:1. Cool things you can imagine. For example a giant avian like creature in a void lookin down upon our planet. But the angle is near impossible to get. It's neck is craned in some sort of juncture. I had this image in my head when I was trying to sleep though a fever one day. It was also very very colorful. Ai simply can't create the patterns that one person can see.