Why is it that working girls (escorts) are considered to be filthy and low lifes??

Surely if you are working and paying taxes just like everyone else, you should be treated as an equal without the ingrained attitude that society has. According to taxation offices, they are the same as everyone else. (just smarter in some cases). If a person works the same hours as everyone else during the day, and is of clean and sober habits - why should they get such a stigma thrown at them.?