And to further complicate the taxonomy- there are typically two types of adjuncts.
Type A’s profession is being a professor. Maybe at two or more institutions because he or she can’t get a full time position, but this type of adjunct teaches for a living. Type B’s profession is something else. For example, law schools hire adjuncts for courses on Professional Responsibility, sometimes for the procedural type classes or for something specialized- cross border IP litigation, for example, where they are able to “snag” a highly regarded lawyer to teach the class. These are typically highly paid professionals, who teach because they love to teach and because there is a lot of prestige associated with teaching at a law school, but they earn their living as lawyers and the compensation they get from the law school is a negligible part of their overall pay.
You can’t mush together Type A- living on what they earn as adjuncts, and Type B- who do it for the prestige, the kicks, giving back, whatever but who have a well paid profession doing something else entirely. Whether it’s an art auction house specialist in Old Master Painting working as an adjunct in the Art History department, or the aforementioned lawyers- they aren’t in it for the money and they don’t need the benefits because they already have jobs.