Ability to publish gets you to the interview stage, the rest is good old-fashioned politics.

True, but the point is, at the faculty hiring stage no one at all cares about teaching ability.

Adjuncts are still expected to publish, unless they have no interest at all in upward mobility.

Upward mobility to where? If you want a better position -- a tenure track, a job at a lab or a think tank -- sure, publishing will increase your chances. But the university is interested in adjuncts as warm bodies to teach students without all that tenure commitment. Publishing may be a prerequisite for advancement, but it is not a prerequisite for the job they are holding.