Actually, there are several new ideas. One them is that professions restrict their markets when they attempt to raise their fees by adding barriers to entry. Since demand is stable or rising, this creates opportunity for other groups to move in "below." As physicians' time becomes ever more valuable, RNs achieve the status of practitioners and LPNs fill in. Aides are now certified, and so on. This seminal idea was published in 1988. Almost ten years later, Clayton Christensen described in his well-regarded Innovators' Dilemma how a corporate fixation on upselling existing customers assured that less lucrative markets would be neglected, providing rich opportunities for new entrants. The parallel is striking.
Whether you have any interest in his topic, Abbott's exposition is worth studying as a model of effective rhetoric. And the writing is vivid; he worked for years in a large mental hospital, "After five years, . . . I had helped administer several tons of thorazine, mellaril and their cousins . . ."