Or the wrong girl. I think the offer of bare service has more to do with the girth of your wallet than the girth of your waist!
Over a decade plus of doing this, I've been dealt BBFS in every spa I have frequented, including MUSE, Flirt, Seduction, AGS, Perla, S9, eSpa, Pickering Angels, and their little house place.Up in Ottawa... Brass /ALPHA Club, CMJ and Paradise. Don't get me started on the indy's. (And these are generally MAs. not escorts)
And when I say "dealt" I never ever asked for it. It just happened. PS gone amuck, or she just jumped on (and in one case as I mentioned the other day). And I assure you, I'm an older guy, Dad body and a moderate tipper.
I think we also need to also acknowledge that many of the "acceptable" services regularly offered at many Spa, including BBBJ, DATY, DATO and PS, carry a significant risk of an STI as well. What makes BBFS especially taboo, I'm not sure. The main think that makes BBFS potentially risky and BB anal VERY risky, is the possibility of blood exchange. (Use that lube boys!)
Anyway, it's out there and if you never want it, be prepared to push her off on a second's notice.