Sexual Surrogates

So I was looking into Sex Therapy as a possible career choice, but then I came across the phrase "sex surrogates" and I was like hmm???? I found out that there are people out there who legally participate as sexual partners "therapeutically". This includes 'sexual and sensual touching' 'fallaitio' and even intercourse. All under the supervision of a sex therapist. I don't really get it. I'm not really seeing any clear line whatsoever between the role of sex surrogate and the role of a prostitute. One Therapist claimed that it is different because of the intention behind the sexual activity. (pleasure/gratification vs. therapy and learning?) I think they do exactly the same thing. They work with people who have problems in normal sexual activity who pay another person to help them have sex, which in turn relieves stress, anxiety etc. I don't understand why the government doesn't just legalize prostitution in the first place. Wait, I do actually... religion. Another vessel to which religion has used the government to prevent adults from being free to do as they please. Except, I don't understand why there isn't any religious fervour against sex surrogates like there is about abortionists. Anyways.