I don't meet as often as i used to so my experience with the agencies is not as numerous as back then but personally here is my feeling..
Back in the day, maybe it was the parties, being more on merb, and the agencies being in the "building phase" but i felt the customer service was more personal, more open, like i knew those guys. Don't get confuse, i never got discounts or any of these things, but i felt the bookers would "accomodate" me often in term of either outcall, pre-bookings, infos and such. They knew i was someone reliable and rather easy to please and you could see from my reviews that most of my bookings were positive. So even if i wasn't the biggest "regular" by number obviously, i was still seen as one.
In the latest years i feel this "friendly attitude" kinda lost itself. Maybe its new bookers, and since i book much less often (wich even back then was never close to some of you guys, was more like once every 2 months or so) but it seem more "business". That said, it does not mean i had bad customer services either. Last couple times i book either agencies it went smooth and well.
Euphoria and Xo are juggernauts now, they been established for 10 years or so, they know they will get the bookings as some guys said.
When it comes to Vog altough they never said clearly i was "blacklisted" or anything, i always struggled trying to book with that agency. Its been a while i tried again because at one point why beating a dead horse, but the last time i saw someone from there was actually Chloe, as in THE Chloe wich was the one who was with James at first at Euphoria. She became a photographer eventually and unless she still meet her old regulars UTR, she been out of the game. This was in 2018. I tried to pre-book with the agency by text, often not getting replies. Once i was in Montreal already, gearing for plan B due to a cancellation, asked for who still had availabiliies, they gave me 2-3 names, i said "yes i would see xxx at xxx time" and then radio silence. There was like 10 mins left before the time i said i would take, so i retext and said "ok well i have to book someone as time goes by so i will look elsewhere" and then not long after they finally reply ... don't remember what exactly but it was what i would call "du fuckayage" in french. I made plan with another agency by that point cause they replied immediately.
That said i would be more than willing to try again if they let me know things would go smoothly and well.
One agency i had great service every time i booked is Luxury. Its been a while since i didn't book there because i don't have an easy outcall anymore like in 2022 and up until July 2023. The ladies i was interest to see (or see again) the most only popped up late the day before or even same day sometimes wich is already hard to book for an incall, so for outcall its worst due to having to book hotel. But this is probably out of their control.
As for the other agencies either i never used them or its been a VERY long time. Combination of only meeting around 3 to 4 times a year and having an establish list of who i want to meet.