Because it has become fashionable in some academic circles to refer to people in general as "bodies" — black bodies, brown bodies, gendered bodies, enslaved bodies, etc., etc. It's not "a black thing" in particular. But it is true that you're unlikely to find many academic references to white bodies, or rich, powerful, or influential bodies, because this use of "bodies" to mean "people" is usually intended to clarify that human beings in a particular social context have been (or are now being) treated as objects or commodities, not as individuals.
I have misgivings about this usage. First, it is alienating jargon that tends to separate specialists from the general reading public. Second, it tends to reproduce the very objectification it is supposed to be identifying. As Alex Sayf Cummings remarked in his blog essay The Case Against “Bodies”:
To talk about day laborers … as a bunch of bodies ready to be transferred to the back of a pickup truck is, perhaps, to make a comment about how they were treated literally as interchangeable arms and legs.… But to do so is not just commenting on their dehumanization—it is … treating unique historical actors as if they are just what an unfair and abusive system understood them to be: interchangeable lumps. There were some bodies on the auction block. There were some bodies out in front of the punk rock bar. There were some bodies going door to door (sorry, moving through space) to hand out Jehovah’s Witness literature. What is the point of this, except to talk about people like they were things?
Exactly.