from personal experience
1) if you are a regular on the scene and you have never been offered, I would say the reason for that is in your mirror. For myself, without ever actively looked for it, it was definitely there. Possible reasons: a) no, I am not a young 6' 200# hot looking stud, far from it b) girls have said that I am a very clam person and that sets them at ease c) I am 'nice' to the girls; like some guy once told me that he learned through bad experiences not to take girls right after me because 'I use them all up'.
2) most of those occasions were tc.
3) never had to pay anything extra - to even think of offering it afterwards would have betrayed the nature of the 'gift', I think.
4) no, I am not really into the escort scene anymore and don't miss it either. The young bods are good for a 5 minute excitement, after that, they can't keep my interests long enough to get anything done. The real french gf sex, however, that I love!
5) That was a few years back. Now in the last few years, with all the girls competing for customers through offering more liberal services (hell, if they are willing to accept $20 less, they would have customer coming out of the woodworks for even safe servcies, all that they can handled... but...), I would not be a single bit surprised that the claim of being offered that once a month is true.
6) 'Debutant' to me just means not hardened yet (ok, you can label it young and naive if you want). Nowadays, they can get hardened in just a couple of outings and their services definitely are not as good after that. No, not aware that 'debutant' has any hidden code meaning at all.