I would think if a Domme had a concern about disease transmission they would care about the sub himself and anyone the sub interacted with (if the disease they were worried about was transmissible to others through normal contact). Plus, if the sub ended up sick then being married would actually be a better thing since they would gave someone to help take care of them since the Domme certainly isn't going to do that (and I do believe that Dommes do care about the well being off their clients).

I am naive when it comes to this subject but I would think the diseases you would worry about from this activity wouldn't be transmissible to anyone else who wasnt literally consuming... Just like getting sick from eColi isn't a risk to anyone who doesn't eat the same thing. But, even if something was transmissible to others through contact wouldn't that same concern be there for people the sub was dating? Which, if not married, could actually be multiple people rather than just one?

I still don't get the specifics of why the marital status of the sub would be of concern for this specific activity above any other session activity.