I like image textures because–though I may not be the best artist yet–I can mish-mash hand-painted work, stock photos and choice bits of procedurals to make whatever I want, with all the chaos and spontaneous organic detail that the infinite-strength rendering engine of ‘the earth’ can provide my imagination and camera with, on any layer. Specular colour, strength and sharpness–colour, reflective diffuse, bump–anything can look like anything, so the wild contrasts and complementary strengths of the different channels can make anything look like anything. I may not be the best, but I’ve seen them.
EDIT: Also, Cyborg Dragon: I know you just started this thread because you’re sulking that people thought your procedurals needed work. Oh well, you might as well get a straight, unbiased answer.