Much abuse in the academic world is directed against students. They are in an ambiguous position. They are often not considered working professionals, though in practice they are. I.e. they often teach and/or conduct research. They are usually not rewarded financially in line with their training and skills. They cannot easily move to another place till they have completed their degree. Also, they are more dependent on their mentor/supervisor than a working professional would typically be. And they are not accorded the rights that working persons normally are. Students are also less likely to complain because they need to have good relations with the faculty for their future careers. Often they are working with faculty members on projects. While similar situations/circumstances can arise outside academia, this combination is relatively unusual. The closest analogy I can think of is the institution of interns, who probably also endure abuse, though their stays are usually much shorter.
Anyway, this is fertile ground for abuse.
While this is not directly relevant, it's symptomatic that there is often much controversy/difficulty when students try to start Unions to protect their rights. This has been an issue for a good many years, at least in the United States. There was a famous case at Yale some years ago, for example.
Additionally, the institution of tenure is quite rare outside academia, though it exists. For example, judges have tenure. Tenured professors are hard to fire, and therefore are more likely to get away with abuse without consequences.
There is another issue, which is more speculative. But I'll mention it, anyway. This may also be country dependent. Foreigners entering Western countries, at least, are subject to employment restrictions. There is one notable exception to this restriction - namely educational institutions, which means universities in practice. This may not be universally true, but for example in the US, being a student is probably the easiest way to enter the country, and the main exception to the H1B work visa cap, the last I heard, were educational and non-profit institutions.
Anyway, in practice this means there are many foreigners in Western universities, both at a student and post-doc level, and of course at faculty level. Here I am only concerned about junior temporary employees like students and post-docs. In the US, at least, there is much institutional discrimination against such persons. They can't easily move to another job or university because of employment restrictions. Getting a non-university job is often very difficult. Getting employed involves an additional burden of paperwork. So, such people are, again, targets for abuse. This is not theoretical - I've seen and heard much to support this. Of course, foreigners get employment outside academia too, but for the reasons I have discussed, I believe the density of foreigners employed is particularly high in Western universities.