When you book with an agency and let's say Amanda isn't available, the booker will suggest Tina instead - you have no time to go filtering through reviews to see if you will like her or if her reviews are good.
It's true that bookers do that, but most experienced hobbyists already know what their plan B and C are, and they reject the booker's suggested plan B. In some cases, there is a plan B with the same agency, but not always. On my typical trip to Montreal I will have a list of about 5 ladies and I just go down the list in order. If I go through all 5 names and nobody is available, I think on my feet and scramble like a quarterback does when he is under a heavy pass rush. With internet, laptops and smartphones this can be done, once agencies post their schedules.
These are the things you learn to do. You dictate the action, you do not let others dictate what the action will be. Bookers are just going to throw at you the girls who are available, and they may not be your type. It is up to the hobbyist to be prepared to have other ladies who are his type that he can go to in a flash. Having an indy backup on standby is usually harder; the indy has to be plan A.