I'm choosing to believe that the question is coming from a place of genuine curiosity. A lot of people don’t know how relationships intersect with the work, and it’s fair to wonder. That said, whenever I’ve been asked this by a client, it has almost always contained a subtle second layer that isn't necessarily neutral... which is totally human.
First, with respect to how many providers have a spouse or significant other? How many licks does it take to get to the center of a Tootsie Pop? The world may never know. But I can think of a couple dozen providers who are partnered or married and an even split on whether they are partnered/married to men or women.
Second, I'd argue most clients know what this is, and still for many the fantasy that's created rests on a kind of exclusivity. Knowing a provider has a partner can disrupt that because it reminds them we have a life outside of their fantasy. It rubs up against the ego in a not so good way and brings the fantasy back to earth quick, fast, and in a hurry (re: “this is a service"). But that's normal because we're all human. And I've been honest enough times to recognize it and the look of disappointment instantly. But on the other end of the spectrum, some men have the opposite reaction. They’re turned on by the “hot girlfriend who cheats” dynamic, the home-wrecking storyline, or the idea of sending me home to someone else afterward. So same question... opposite projection. I digress.
As for me, I’ve had two long-term relationships during my time in this industry, and both were great and super supportive. Were there times that were made more difficult because of my work? Absolutely. But they knew their limitations and they knew how to communicate, and we ended because we wanted different things. One partner wanted to relocate to the Deep South; I didn’t. I may be from there but that doesn't mean I want to go back. The other wanted marriage and children. Frankly, I’m still too selfish with my time, money, and freedom to step into the role of "wife and mother" now or in the near future.
Anywho, in my opinion, the real question behind your post isn’t actually about a provider’s romantic status. I think it should be about how the fantasy a client seeks intersects with the reality of a provider’s personal life and that’s a far more interesting conversation.