They have the tools. They use the draw and paint programs. They have cartooning software. They use the internet. The world wide web is full of visual language pages.
Many kids learn best from it.
And editors of modern textbooks have begun to realize this. They are using it because it is superior to text. In many situations. That's why it's so important. In particular it's superior for showing the structure and dynamics of complex systems, which is what a lot of modern subject matter in science, technology, and business is about.