Kanye West and Bianca are definitely doing some humiliation ritual, or this could be their kink; maybe they love that other people see her naked; maybe it turns Kanye on; who knows why they do it.
But fans definitely love it. Bianca was wearing a very thin, fully transparent cloth; nothing was hidden, her booty, her breasts, and her vagina—all of it was visible.
This is also not the first time Bianca did this, but she was mostly showing her breasts before.