As I understand it, it's not so much that it's desirable to fall within these categories, it's just noting that these privileges *exist*, and that people should be aware of them.
For example, as a formally-educated cisgendered femme Caucasian-appearing woman, I have certain levels of privilege that my Puerto Rican cisgendered butch female friend, who speaks with a noticeable accent, does not. (She actually has more formal education than I do, but someone observing us wouldn't necessarily guess it if they were listening to our manner of speaking.)
This doesn't mean that I'm necessarily taking ADVANTAGE of this privilege in any way, but since we live in a society based on kyriarchy model, I am perceived as having more privilege than she does.
It's not so much that this model exists in all individual relationships, but more that society privileges certain relationships and certain people over others.