here are some thoughts (perhaps i can make up for my embarrassing attempt earlier!):
a. if consent is defined/understood as conscious and explicit permission to engage in a particular act or interaction, then it gives too much power to consciousness and verbal clarity. our consciousnesses are (i would argue) a small fraction of how we interact with the world [and are (perhaps?) the most easily controlled and manipulated--eh, i'm not sure i agree with that, but i'll leave it there anyway]. communication is confusing even when nothing serious is on the line and we've known someone for years.
b. if consent is understood as either explicit or tacit "going along with", then it is so open that it becomes useless as an idea.
people who rely on consent as a way to address power dynamics, lack of self defense information and/or techniques, and confusing cultural differences, are emphasizing a. but that option assumes that everyone is weak and needing protection; it assumes fragility and emphasizes danger. it seems related to the social stereotypes of over-protection, from everything being marketed as antibiotic, to parents being prosecuted if they dare to allow their children out of their sight.
i am trying to stay open to how it might still be useful, and the best i can do is consider that these terms are not that different from other political jargon that has come before, that it is just a new language that people will learn to maneuver and negotiate through; and that really may be the case.
this may still not be addressing anok's question, but...