Because if I call her

She will here the porn playing in the background!

I, for one, don't screen via phone.  I set up all new clients via email, and returning clients are welcome to text message me or email me to schedule.  I do, however, require a phone number for screening purposes (though I never contact anyone via phone without permission).  

For me, personally, calling can get sticky.  I'm rarely in a place where it's appropriate to take a phone call of this nature, and I'd rather not anyone be able to hear what I'm discussing over the phone.  I'm sure a lot of guys feel that way too.  Again, its all about comfort levels. Also, exchanging information via email ensures that the session date, time, and place can all be easily found and referred back to.

I've seen only a small fraction of the full service providers out there. But I cannot recall a one that did not use some variation on the two-call method for incall. The first 'call,' to name the hotel, could be voice, text, or email. But the second call, upon arrival, to get a room number, is always either text or voice. So a guy is gonna have to give up a phone number at some point. It's one of many reasons an anonymous, well-secured, hobby phone is so necessary. If your client is full-service, I don't see why the guys are balking.

But, again in my less than universal experience, massage providers are sometimes less stringent. Some will give complete location information days in advance. No phone call is ever required. So maybe some massage-only guys could get along without a hobby phone. If your client is a massage provider, that might be the problem.  

And then there's the flip-side question. Why does she insist on a phone call or text before booking? If she insisted on a phone call, I could think she just wants to hear a voice for some reason. But what can she possibly get from a text that she doesn't get from email, apart from the phone number? It's unclear. When faced with demands I don't understand I get a little nervous. Maybe that is part of it.  

Booking a first meet is always a bit fraught. I don't see the point of putting up roadblocks. But everyone needs something different to be comfortable. I've seen providers who use the two-call method and want to know the number you will call them from, but still won't give up their own phone number until an hour before the appointment. Maybe it's a timing issue for the guys, also.

I personally prefer to do the initial contact and booking by email or pm but if she wanted a call or text I would be fine with that.  What kind of response did they give when they were told she wanted a call or text first?

I hate calling for the intial contact!

I miss lots of ladies because they have no email and don't want texts. I usually set things up from work, so calling is just not an option. Booking from the car always sucks and booking from home is just dumb.

I prefer to email or text to find out if they are available at the time I need. I have no problem calling from the car for the second call, but many of the ladies send everything you need to arrive at their door without a call ever being made.

With a good ad and reviews, there is no need to call or worry about the content of emails or texts. I should know the rate and menu (FS or not) before I get there, so my written communication is only about time and place, never money or services. There is nothing illegal about arrange to meet someone.

IMHO, more ladies should do business by email. It is way easier to have a burner email than a burner phone. And yes, burner phones suck for texts.

... who wants to talk with new clients on the phone before meeting them. The provider works with an assistant and the appointment is confirmed before the phone conversation. The purpose of the phone call is to "break the ice" prior to a first visit, so the session can get off to a good start. The call is scheduled at a time that works for the client and provider.  

I like that approach and wouldn't mind doing that kind of call before an initial session.