I only use ambient lighting at any venue I shoot in, no matter how dark, dingy, dungeon-esque. Part of being professional is not tailoring your environment to your needs, and capturing the action as it happened.
The art of the master craftsman, you mean? Agree totally, location lighting a copout? Although, if I am sent to do a job, if necessary I will compromise my ethics to get the pix. Guilty as charged.
The way I see it, I would have no need to compromise my ethics, because if I can see the action, I can capture it as it is. Plus, even when it might be more convenient to use a flash, there's no way the timing the can compare to available light. Either way, you can be sure that if there aren't lights to work under, there probably won't be any money to be made, either.