Honestly, I can see what you're talking about. Why does a regular client all of a sudden drop a provider when she offers bbfs to him, instead of continuing to see the provider and using protection?
I'm not sure. I feel like that offer might shock a lot of clients, especially if they've never asked for it. The assumption would be that "if she offers it to me, she probably offers it to others". It's not something that's special anymore, maybe? Knowing, pretty much fully, that she offers and gets paid for bbfs at all could be enough of a boner-killer for lots of clients. They might also assume that because she offers bbfs that she's "dirty".
When you're dirty, you need a shower. When you have STI, you need treatment, not a moral judgement.
These guys are probably assuming some age-old "well, she's just another dirty hooker" crap. Fact of the matter is, she's not "dirty". She's got different limits. If she wants to offer that, that's her choice. If he wants to accept or reject the offer, that's his choice.
I would be hard-pressed to find anyone, civilian or otherwise, who has never had bareback sex. It happens. Condom usage is always over-reported because people know they're supposed to be safe, but often aren't