This is likely going to be a wildly unpopular view with the ladies, but the simple fact of the matter is that most people tip for a service and not for a product. Unfortunately, most ladies, although they seem to believe they are providing a service, usually feel like they are delivering a product. No woman will ever agree to this, no matter what you say to them. The short answer is that I never tip for anyone who seems to me to be providing a "product". If someone steps outside of the routine box and actually delivers "service:, then yes, I will tip. The dividing line, and what no two people are ever going to agree 100% on, is what delineates the two. Many SP's while protesting otherwise, will say that they don't expect a tip, although it's clear that many do. Some will even ask for a tip in advance.
This is such a fluid industry, with such a marked individual experience. that's it's really impossible to define what means what to who. There's too many variables. What I will say is that a tip is not an automatic occurrence.
With a taxi driver or a waiter the product is either the ride or the food, and the service is that extra degree of personal comfort and interaction beyond the product. With SPs the product is sex. many SPs expect the tip based on the fact that they've had sex with someone. Sorry, but that's just the product you're selling. The personal interaction is the service. That's what gets the tip.
Please bear in mind that this is a gross generalization and is not necessarily directed at any individual on this board. The advertisers here pride themselves on above average service, and may very well be entitled to more consideration than is normally the case with SW's or some Cl ladies. That doesn't change the concept, just maybe that the demographic that's targeted may be more outside of the site group than within it.