Story code: Humiliation

[Ranai]

In the BDSM Library's excellent and very handy list of story codes, there is one item called 'humiliation'. It's not an enormous favourite of mine or anything, but I have a question about its classification. Both in the advanced search and in the story codes humiliation is listed under the heading Level of Consent.
This left me scratching my head and idly wondering...

Why on earth is humiliation a level of consent?

The other items listed under Level of Consent are:
romantic, consensual, reluctant, mc: mind control, blackmail, torture, nc: non-consensual.

Does the fact that there is humiliation in a story say anything about its level of consent?
Not to my mind.
As far as I can see, humiliation can turn up in a text under any of those levels of consent?

Perhaps it would fit in better under the heading Fetish?
Any ideas from the able writers and avid readers?