Besides being able to identify us when we meet, what are other reasons why a provider would ask to see a hobbyist's pic before agreeing to meet?  Is it a way of screening for race, age, and/or appearance?

I do know that there are some providers that do. I think they offer it as another form of Verification & Screening. If it's not your bag of chips, then don't do it.

I guess to see what you look like before agreeing to meet. Similar to how some ladies ask for a physical description.

I think some use it as a form of screening, and some just want to make sure the guy in the peephole is the guy they have been communicating with.

she might want to make sure she doesn't already know you from "real" life. It happens.

I know a few women who have this requirement, but would never do me much good. If a guy is lying to you about who he is, I doubt he would send a real pic anyway, and if you are going to waste your time driving out to him or getting dressed for him based on a photo, well I feel sorry for ya.  

Still, very few ladies actually ask for photos, and very few guys would send them.

I don't ask for photos of a gent prior to first meeting and personally don't think its a great idea for you the gent to do. Small world...what if you send a pic and its a lady that knows you in your private life etc. If you arrive and you recognize a lady you are both on the same playing field. I do ask for physical description when I send out references though. That is for safety. If I am told a 6" dark haired gent is David do little by the provider that gave reference and a 5"9 blond gent shows up I know don't even open door. Sadly there are A FEW gents that go to great lengths to avoid screening etc. I have also had ladies send me a reference request where the gent says he met me and I have never met. So gratefully most hobbyists are wonderful but the few bad apples make it imperative to screen well and physical descriptions are part of it. I do not ask for photos though and would not send if I were in your shoes. Many beautiful ladies to choose from, not worth risking YOUR privacy/safety.