Prefab, and technologies that reduce labor. It won't eliminate labor completely, but will reduce demand.

My house is full of copper plumbing, all cut and soldered together by hand. The wiring is all in hard conduit. Today, conduit is gone, and plumbers assemble things using flexible tubing and fittings that get squeezed onto the ends (for lack of the correct terminology).

I doubt that fixing things will ever provide as much work as construction.