Hardscape-only tanks w/dark substrate?

Hi all, I've been admiring the trend in hardscape-only tanks (rock and driftwood) aquascapes showing up. But I've also noticed that all of them contain PFS or light colored substrates...none in black. Does anyone know why or is it just a coincidence that I haven't seen darker ones? I hope to set up a new tank in this style in the coming month and prefer a darker substrate to show off my silver tetras vs. them looking a bit washed out against a light background. If anyone has seen photos of dark hardscape tanks, I'd love to see them! Thanks!!