Why does Thoreau say people should build their own house?

Thoreau suggests that if men built their own homes, as birds build their own nests, "the poetic faculty would be universally developed." The profession of architect he finds to be an unnecessary division of labor, for it is natural for a man to build his own house and allows him to think for himself. The appearance of a man's house would mean something if he made it himself and put his spirit in it; without his spirit, it is only a coffin.