A GitHub blog, usefull to me, hope the same for you.
“Generative art” often refers to algorithmic art (algorithmically determined computer generated artwork)
This is a very convenient explanation for non initiated audience of what people are doing here on Shadertoy.
This is art, a very well known addiction about beauty.
It’s beautyfull to make short programs generating fascinating images.
It’s beautyfull to understand the mathematics that allow to generate these images.
It’s beautyfull to understand how our vision is working and tells us informations about the world.
Colors, Lighning, Motion all what our brain needs to understand what we are observing on screen.
Hope these few lines may help to explain what people are doing here, and why they are spending an unreasonable time with it.