Your psychotherapist is absolutely not supposed to have sex with his / her patients, and doing so (and getting caught) is grounds for losing your license to practice.
That said, about 30% of psychotherapists are banging at least one of their patients in the United States...or claims to be...or something. If we're lucky that is a bogus stat, but frankly it's plausible.
That said, ideally you'd get therapy and sex from different sources.
People are people. You're not supposed to date/have sex with co-workers in most workplaces but it happens all the time. I'm not saying it's a good idea for people to be banging their therapist.
In 1980s psychological parlance, the most common places to find partners were:
Work
School
Church
Friends of family
Friends of friends
In the 1990s and aughts, we were already seeing that things had shifted. Fewer people were engaged in their church group. There was more awareness of sexual harassment at work (and power dynamics that could interfere with regular human interaction). People also had fewer friends and less contact with their extended family. This resulted in more people clubbing (and functioning by one-night stands) and otherwise looking for better places to find eligible partners.
I was in the psychiatric sector both as a patient and a peer counselor, and they recommended activity groups. Frisbee golf, knitting, puzzle-building, backgammon, gardening, etc. I sucked at those, but I was dating during the golden age of Craigslist personal ads. We still have sexual harassment in the workplace in 2024, often from upper-management on the clerical pool, which means for anyone not in upper management, they're being micromanaged and kept from propositioning fellow employees. But curiously in the 1970s and 1980s employees often dated and married.
I, for one, am completely down with the Aldus Huxley idea of creating a community system that allows everyone to get laid and get psychotherapy (id est, vent their troubles and get professional feedback). Huxley had to dystopia it up a bit with compliance drugs and criminalizing intimacy (and abuses of genetic engineering) since he was writing a cautionary tale, but I think if we did these things and then upgraded friends (or created a subset like BFFs) to include emotional intimacy, it would make for a pretty groovy society.
Right now, we are really far away from this notion, and are about to confront some great filters unprepared, so coulda, shoulda, woulda.
I actually came across someone that offered that service once, they were working in the same co-working office as a colleague. They had flyers and everything.
I guess? I mean, I go to a venue, get a drink or two, meet my friends, by now I'm probably already undressed, then we have sex, with whoever I feel comfortable with. In the meantime there are at least 60 other people in the venue doing their own thing, BDSM shit, sex, whatever floats their boat.
Really nice vibe, everyone is respectful, consent is important.
After having relationships just for sex and/or the therapist part for both me and whatever partner it was at the time, I'm done with those kinds of relationships. I do want a significant other, someone to really share a life with for the long haul.