Thanks for your comment. You are right, that is a thing, unfortunately. However, there are certain instances in which a person cannot give consent. For example, if someone gives consent because of coercion (blackmail, external pressure...) it is not a valid consent. Legally, if a person is not conscious cannot give consent either (for example, when sleeping or drunk), even to a spouse. Besides, even BDSM has its legal limitations: nobody can't consent to get seriously injured. Here is an interesting article about that. How many sex games actually depict affirmative ongoing consent? Most of them don't, showing some kind of coercion, threat, abuse of power... to get the victim's "consent".