Second, "bullshit" in "bullshit jobs" doesn't mean useless from market's short-sighted POV. A competitive market is prone to formation of negative-sum games between companies, and further to formation of more companies supporting those games. Consider the advertising industry, the poster child of wasteful negative-sum games: in saturated markets, it supports competition for fixed customer pool. To that end, it employs countless of creatives designing new texts, posters, videos, etc. It then employs printing shops and distribution centers to place all that material in the real world. All that effort, man-hours and fuel is wasted - in an attempt for one side to get more market to themselves, only for the other to cancel it out. If all parties agreed not to do this, everyone would be better off. But they can't, and so instead a whole industry of bullshit jobs is created.
Those are, I believe, the two main sources of bullshit jobs - internal closed loops, and negative-sum games.
(EDIT: in a sense, those two are actually facets of the same phenomenon.)