As others have already stated, this depends on the provider and the client.
I'm always distressed if a provider puts a condom in her mouth before she has put it on me orally. I don't want her body fluids inside my condom, just as I'm sure she wouldn't want my body fluids. So, when that happens, I quickly tell her to use another condom but this time don't put it in her mouth until it's already completely on my penis.
Have I had bbs with any providers before? Yes, but they were unintentional experiences because the condoms broke and the bbs time was minimal since most of us can tell when a condom breaks. Was I still concerned? Of course, for after such breakages, I would go to my doctor as soon a possible to get STD tests done and breathe sighs of relief when the test results came back negative.
Still, that said, some providers offer or some clients want bbs because the sensations are much greater than those with covered sex. But are the possible prices like STDs and HIV beyond the immediate experience worth it?
I would be very leery of any provider who offers bbs since that would suggest to me that she might already have an STD or worse and doesn't care if others get infected as well.
Be safe out there.