If nobody can buy your land or trade your capital, what do you really have? We need the value produced by labor for there to be a market for anything else.
But this requires initial capital to get going, and that capital (and land) is what gets traded. At some point, when capital is no longer required, then it would become worthless, but by then i think humanity would've reached star trek level of post-scarcity (or killed themselves with a war).