Just speaking for myself but it's fear of intimacy which causes this for me. Sex with a working girl is just that, no consequences after, no arranging to meet up again, no texting, all that stuff. The last time I met someone I liked and we decided to have sex I found myself having to imagine I was having sex with someone else, a porn star, a working girl, other things to keep myself stimulated. That was even though she was attractive. I just don't do intimate relationships anymore.