Here's my cut at it:

Fractals represent a new symmetry: dilation symmetry. That's when something looks the same at different scales. (The property of dilation symmetry is what makes MojoWorld possible; planets that you can get as close to or far from as you like, while maintaining essentially perfect detail.)

Symmetry is ubiquitous in art. The human brain is a pattern-recognition machine; fractals represent a new class of patterns we've recognized.

So it's utterly natural that artists would seize upon fractals an run with them, so to speak.

Why? "Because they're there." :-)

-Mo

PS- In case you didn't know, I was Mandelbrot's right-hand man for 6 years, so I know a bit about fractals. He even credited me with being "the first true fractal-based artist." Not trying to brag; just to establish that I'm not just shooting from the hip here. ;-)