This is actually one of the of the things that comes up time and time again here. If you want a telephone connection with a lady, it makes sense not to chase after someone whose ad states "text or e-mail only"! When you push the issue, and receive a curt response, I don't think you should feel high-and-mighty, I think you should question your motives.
I am happy to answer any and all questions, by phone, text, or e-mail, when I'm able, and when the inquiry seems legit. If a call comes in, and I'm not in a position to answer it, I will typically reply with a text, explaining such. If a text comes in while I don't have my phone with me, I'll often reply later, explaining such. E-mails always get a reply.
Exceptions: I almost never reply to a caller that has contacted me between midnight and 9am, because I presume that they're looking for something I don't offer. I've been advertising Daytime Playtime for long enough that I just don't feel like explaining that any more. If someone is calling at that hour, by the time I replied to them, they'd likely have found someone else anyway, so I just don't think it's important that I reply, nor is it expected.
In reference to the OPs irritation at those who contact frequently but never book, yes, I think that just goes with the territory (due to a variety of factors, all mentioned elsewhere in this thread). We all need to find a way to make and defend our own boundaries, while still being open enough to engage the serious inquiry. This requires an exceptional array of skills.
Maybe someday, I'll own a massage parlour. Should that happen, Vancouver pooners would enjoy a level of service previously unheard of. But that's another chapter to my life, which has yet to be revealed!