At one time, you couldn't get work with an agency, if you didn't measure up to a certain standard because they figured the guys would not want an ordinary girl-next-door type. I know, because I had a friend who was an escort in Toronto in the 1980s and it was brutal.
In 1995, was told I was "too old" when I started at age 35, but the agency owner, liked my attitude and advertised me at 29. Then I convinced her to let me advertise my own age, and "boom", lo and behold guys actually wanted to see a bigger, older woman (I weighed 150, then).
We were basically told not to kiss, allow DATY and for duos, we had to use a dental dam (which to us, was a condom cut open). If they found out you did anything you weren't supposed to, you got ridden out of there. In-calls were unheard of, so if the agency owners didn't like you, you didn't work.
The Internet paved the way for being able to work Indie and thus us ladies being able to provide the services we felt comfortable with. I have always been pretty open and always allowed kissing and DATY since 2000.
As far as the model looks good, I have met very few ladies who actually fit that bill, so even when there were standards, it was subjective.
I think it's really about the whole package, looks just being one aspect. I truly do believe that.