even though you don't have to be with a high fashion agency to get modeling work, it is sometimes nice to know the opinions of photographers who work with them.
A photographer I know and worked with doesn't use social modeling websites or Craigslist and these are his reasons.
He says it is tradition and that he feels if a model is pre-selected by a modeling agency they will show up and usually be legit and worth it. Agencies such as Ford, Wilhelmina models, MC2, Trump. (Photographers are given a password and they can scope out the models, and the photographer will put out a casting when they are looking for models, it is for something, a project.) Or the casting director and production company picks the model through the agency or through casting.
So # 1 is legit. You will get a model that is serious.
# 2 you are trusting the judgement of the bookers who pick girls who are current looking and that there is something about them.
#3 if she is with an agent she is legit, a real model.(otherwise it is like going to the mall and finding a real model and good people to work with.)
Sometimes the original is busy or has a go-see, or gets booked and then another girl comes and she isn't as good.
This can explain why being with an agency is better because you can get exposed to people/photographers at a higher level.
When actors don't have an actor or agent, they are not exposed to levels of castings and breakdowns compared to if they were.