Nobody likes a toothy blowjob, I know I certainly don't. Why is it that some girls give toothy blowjobs? I have only met a handful of hookers in my life that can give a proper, sloppy blowjob with sensation of no teeth at any stage during the act. I would agree that most hookers give better blowjobs than Civies and in my experience of seeing some girls outside of the escorting world, I would certainly agree with that.
But the questions I have is -
Is it just down to practice to improve on how to give a proper blowjob? Or do they need to have some training? 
Depends really.
For some it's lack of practice, ignorance, too small a mouth for the cock, too thin lips to cover teeth. And for others it might just be they don't care.
I manage to avoid getting a cock grazed on a tooth for the most part. But occasionally it happens: too thick so it grazed my molars, or stupidly aiming for the roof of my mouth and driving my upper teeth deep into my lip (at which point I warn then uncover, my mouth goes back, not up into my nose).
Blowjobs are surprisingly more complicated than people think, it's not just covering teeth, but how fast or slow, deep or shallow, tongue action, tight suction or loose, swallow spit or let it drool, then managing breathing. So if someone is inexperienced teeth might come more into play if they're trying to work out when to breathe.
Or you've just got too pick a cock for their mouth.
Alternatively, if your cock fits through one, you can bring a ring gag to your punts, allows SPs to relax and not worry about teeth ever getting in the way
