Simply put, I am less worried about my family finding out then the rest of the town.
What you have to understand about hwere we live, which my Master, fortunately, hasn't had the displeasure of seeing as of yet, is that this town is very prejudiced when it comes to people being "different"
And example, if I may. When I was in high school, I had a best friend from Equador who's mother was a lesbian and even had a live in girlfriend. My friend was ridiculed, beat up, and even by her teachers, ignored. They figured that because her mother was a lesbian, so was she, and because I hung around them, I was a lesbian too...almost as if it were some disease that could be caught. Eventually they were run out of town. No one would give them jobs. They had no choice.
So, knowing my town, and I can recount many such stories, many of them recent, people "finding out" would be bad. I would probably lose my job, and my parents and my brother's family would be affected as well.
I withold my life from people, not out of humiliation (because I don't get embarrassed or humiliated easily) but I do it out of repsect and concern for my family. To do these things with out regard for their safety would be reckless and selfish and I refuse to do that. I will not risk damage their reputation for my own "pleasure"
Now this may seem a little far fetched or perhaps in the dark ages, but I know my town and I know the people. While I think my family might be tolerant of my choices, there are many that would not be. So I keep my business private, and it anyone held the threat of public exposure over me, well I would have a serious lack of trust for that person and would be hesitant to do anything submissive. ..especially if there person involved already knew of the conditions and the workings of the place.
On the other hand, in a city where no one knew me, I would more than likely be a little more willing.