3D Printing and the Future of Architecture

Minnesotan man builds the world's first 3D printed concrete castle in his own backyard, designing a kit that can print two-story houses

This castle strikes me as interesting because of what this technology might lead to. One reason that architects lean toward sparsely decorated buildings is that decoration is expensive. Can 3D printing make a contribution here? It seems to me that we could easily design elaborate friezes, pediments and other architectural elements on a computer and then either 3D print the designs into concrete or 3D print durable plastic molds that could be used to cast pieces in one of those high-grade forms of concrete that looks like stone. Why not?