SIS: a lot of hard work.
That's why the Romans got somebody else to build the Aqueducts for them. There's a lot of tedious work in old style building. You're probably a Celt, content with mud & straw. One requires slaves, that is those working for food, shelter & clothing.
The Neoliths beat the sandstone with large pebbles. One needs to plant more than is necessary & defeat enemies to acquire slaves.