The juxtaposition of the smooth man-made surface and the organic "natural" plateau is an intentional aesthetic feature. It's been part of eastern art for centuries and more recently western as well. I differentiate between the Scandinavian freehands, which aim to mimic nature, and the more recent ones that combine highly architectual/sculptural shapes and natural forms. There are pipes that are meant to look like you've picked it up from the forest floor and others that are undeniably shaped by a human but with "natural" portions left behind for interest. Both can be hard to achieve.
Picked up from the forest floor (Ben Wade):
Juxtaposition of human and natural (Pan Langjiang):
A bit of both (Kadesh Swanson):