It's a line that is crossed, using your body for money has never ever been seen as something normal. Even accepting the reality of life complexities, broken marriages, loneliness, etc sex as a products is never praised.

The only argument so far is "I should be free to use my body as I will". But probably only a minuscule amount of sex "workers" have the material and emotional comfort to choose that.

So basically when other industries are often exploitative, it's probably a few orders better than prostitution, leverage a bit less immature or broke people.