Escorts will have various reasons for not having face photos up, I do (probably too many, I have no shame), but belle de jour proved I don't have much to worry about in my current field of science, plus 20 to 40% of scientists have done sex work of some form (at least where I work).
Similarly most of my friends and some of my colleagues know what I do. However other providers may be more cautious, to avoid friends/family/colleagues finding out what they do. Especially with posts here saying how to save private gallery photos. Just try to go by someone reviewed here until you get a feel for how to tell bullshit from true.
At the end of the day, if you book them without a face photo and you don't like how they look, you're perfectly entitled to walk. It's not that hard.