Construction sites are always muddy. Kitchens are always messy, at least while meals are being prepared.
People want assembly to be antiseptic, and free. It ain't. It takes time, and skill, to fit materials to the site, and the task, and craft them into an integrated whole. People don't want to live or work in prefab trailer park modules. They want real homes, real stores, real offices.
I've been re-reading some of Christopher Alexander's work, and remain skeptical that either good buildings or good code can be seamlessly, effortlessly conjoured up out of Lego blocks.