You tip your waitress because she is making 2 or 3 bucks an hour, and she lives on her tips. Why restaurant owners are allowed to do this is beyond me, but that's the system. Now I see a lot of tip jars sitting on the counters at convenience stores and the like, I guess those employees figure that they are making minimum wage, so why not shoot for a few extra bucks?
In NYC, and other big cities as well, I suppose, everybody has their hand out for a tip, and if you don't tip well those that you will see more than once, you risk serious repercussion.
Why would you "tip" an escort that you have just paid 300-400-500 for an hour? IMO, the only answer is that a) you are wealthy and b) they have gone way above and beyond what you expected. So you can't give that tip in advance. I take it back, the other reason for tipping in advance is to impress the girl and hopefully improve your upcoming session. Of course, that will only work if she counts the envelope beforehand.
The only escort that I would EXPECT to tip is an agency girl. The best agencies don't "require" tipping, but you know that they are taking a healthy chunk of your donation, and if the girl is attractive and skilled, I would really want to show my appreciation. I'd probably tip 20-30%, at the end of the date, based on her performance.
"SHOULD" you always? If you expect to see the girl again, and you can afford it, then it's not a bad idea. But you don't HAVE to.
No, you do not have to tip. It's always appreciated but not ever required or expected in my opinion. I do think that if you see a girl through an agency that tipping her is important since the agency is taking a percentage and she may have to pay for the room as well. I just think it's kind to do in that situation.