Audio samples give you a great first impression of a lady's ability to get into a scene. You're all a very talented lot, I've heard samples from competition that sounded as if somebody was reading the news (without that being part of a fantasy). If that's the attitude with which a PSO records her sample that so many potential callers will listen to, it's very likely she'll be doing a grocery list or reading a book during our call.
In a positive way, it gives you a good idea who might be the right one for you to call, probably far more than the little texts. It's certainly a much bigger turn on for me than some picture (which in most cases won't be the person you're talking to anyway, I dare say); I'm here to do phone sex, after all, not webcam watching, so why should I care? (I mean, of course sexy pics are nice, but for phone sex other qualities are important to me).
The generosity with which the ladies here share recordings with us and the attention to detail that they mostly pay in them is a huge turn on and one of the reasons that made this place stand out for me and has me coming back for more instead of moving on. But not only that, I also think it's very wise business strategy; of course you'll get the occasional potential caller who'll instead just get off on the recording; but most of us will be inspired (read: extremely turned on) and want more, always more, and only the mistress' live voice will do.
so I'd say it's mutually beneficial...
on a related subject, one amazing lady that I recently had the (sadly interrupted) pleasure of talking to on the phone and chatting with online pointed out during the latter that she wouldn't chat when on the phone, and I think that's commendable. I know at the end of the day for most it's just a business, but even so dedication to quality is very much appreciated.