Yea, I worked in the professional photography field for many years. A large percentage of the models are just a girl that has gotten by on looks all her life.
We worked a few favorites that were normal women and were true professionals. It is amazing to see a real model smile on command and make you think she just saw the love of her live. A 100% real warm smile on command.
One big shoot we did was for a casual wear clothing catalog. A swarm of ladies came in and took over the ladies bathroom - dressing room and made a HUGE mess. They would go back in there to change clothes and throw the clothes on the floor.
We did not ever hire that modeling agency again.