Chesterson's Fence at a corporate level.

> There we would not see "spare labour" because it would be competed-away.

This only works (reliably) in an idealized free market.

That is to say, in the classroom.

In the real world, there are a myriad of reasons in any given situation why a company might have a low profit margin, but still have loads of inefficiencies and other imperfections that haven't been, and won't be, "competed away".