Presentation. Escorts wear nice clothes, speak the language properly, and are talented enough to pass off as a wife or girlfriend if that's what you're looking for. They can roll with a wealthy business crowd and not stick out too much. Just good ole' fashion market demographics at work. I'm sure some metric of success among the people who use their services is to brag about how much money they spent on a high end call girl. No different than bragging about your new $60k car in the driveway.