No should ALWAYS be enough. With everything. But we are also trained, especially as women, to 'soften' the no with an explanation.

It definitely seems to be more a thing up here in Washington than it ever was in California, but I'm not sure why. Though the guy who brought me booze when I said no was in LA. He was one of those guys who walk around with a shots holster whose ONLY job is to get people to buy shots, and the others at my table were getting them, which is probably why he felt okay going that extra step. :/