I truly wish I knew the answer to this question. I mean I could give the basic "because it excites me and makes me horny" answer, but I know you are really asking why does it do that and I have no definitive answer.
As far as I can tell, it started with the first time I was cuckolded by my former high school sweetheart when I was about twenty and ended up being in a very perverse and emotionally damaging relationship. It took decades just to come to terms with it and learn to accept myself and the desires that I developed during that period of my life.
Perhaps I became conditioned to associate being humiliated with pleasing my owners and making them happy. For a submissive, the goal of pleasing one's Mistress and/or Master becomes an ingrained need, so perhaps I needed to feel that shame to know I have done everything and given everything including my pride to please them.
The "bull" in that relationship was an exceptionally sadistic prick who got off on finding ways to humiliate me and break my spirit.
No matter, as the Domme who rescued me said, it doesn't really matter how or why it happened as the past can't be changed, it's only how one chooses to use today and tomorrow that counts and I do have a choice.
So now that desire for humiliation is something I am permitted within the safety of the D/s relationship I share with my Wife, to give myself pleasure, as perverse as that may seem to others.
