Most homes built don't use conduit for electric anymore. A few jurisdictions like Chicago require it. In any case, doing it new construction is quite easy and u

Most homes built don't use conduit for electric anymore. A few jurisdictions like Chicago require it. In any case, doing it new construction is quite easy and usually the job given to the newest apprentice electrician. Plumbing (including HVAC lines and gas lines) already come in standard sizes and can be cut with a saw; connecting them is trivially easy. (HVAC lines might be slightly harder but everything else is easy.) Hanging drywall and mudding it is not particularly expensive and is necessary for good fire resistance. There are cheaper techniques like pre-printing wallpaper on drywall, but most people would rather pay more to have a conventionally painted wall. Metal roofs are already fabbed at the factory. You simply order what you want and install it. Obviously a simpler roofline is less work to install. Solar panels can't be the roof because few want to engineer a solar panel which also is capable of being a watertight, weather-resistant roof tile that can hhandle things like snow load, driving rainstorms, and has the ability to do simple repairs. There have been attempts at this, but then it costs more than just a conventional roof plus conventional solar panels. "3D print" a wall doesn't make sense - where is the 3D printer going to come from and where it will be set up? 3D printing stuff requires having a base, rigidity, and so on; it's just not well suited for putting up walls which is a pretty trivial task to do. Hope this didn't sound dismissive, but the problems in homebuilding that could be solved by manufacturing techniques and automation already have been solved by the people who are in the business of making singlewides, doublewides, and modular homes; it saves a little money but doesn't save that much, and the resulting product is often quite a bit less desirable and less durable than a conventionally built house.