OP is confusing BDSM sex games with D/s (etc) lifestyle.
There are people who will do "anything" within the game because the illusion of being completely at the command and mercy of another person is something they find intoxicating and erotic. Equally there are people for whom the illusion of being in control is erotic etc. That's slightly separate from the idea of playing with pain as an aphrodisiac, although of course many will use both.
But the important thing is that in general this is within the game. There are time or practical limits to it really, and certainly sexual limits agreed in advance. If one or other party feels uncomfortable or wishes to stop or redirect the game then they use code words to make that clear without totally breaking the spell.
Within that framework, then, the role someone plays in real life and the role they take in the game can often be opposite. People whose careers are very pressured and senior can in some cases derive comfort from having certain decisions taken out of their hands; some people who are professionally powerless can use the game to assert themselves and feel empowered.
That is not to say that everyone fits that pattern, just that one absolutely cannot judge from a person's public behaviour what their bedroom behaviour might be - although of course that ought to go without saying.
The issue of D/s relationships - that is, playing the game for real, is much more complicated IMHO and not really related to sex. Taking responsibility for another adult's decisions, or abdicating responsibility for one's own decisions to another person, is not something to be taken lightly. It certainly more closely resembles a parent/child dynamic than that of an equal couple. In normal circumstances I would be vaguely worried that the kind of person who would want to have that real power over another wasn't a suitable partner for someone wanting that kind of control - that in too many cases the situation could be taken advantage of, either by a controlling/abusive person, or by someone trying to escape the real responsibilities of adulthood.
There exist a very few situations where an adult does benefit from having choices taken away - for example I'm thinking of a couple where her recovery from eating disorders hinged on the agreement that he got to tell her when and what to eat, while she physically recovered and learned both emotionally and digestively (?) how to eat normally. But that was a very particular situation and a temporary one.
Does that help at all, OP? For what it's worth, I would struggle to call DH "master" except with a hefty dollop of sarcasm, but I do call him "sir" within the game.
Now I must make sure I nc back very carefully before posting on any of my TIO...