That's a little too purely social - a better explanation might be that scientists care a lot more about being right than the public, because if the public gets something wrong they have careful scientists to set them straight, but if the scientists collectively get something wrong they'll just be wrong forever. As a result the measures of certainty matter far more than the statements themselves, because a mild-mannered truth that is indeed true is perfectly valuable while a bombastic claim in which nobody knows how confident they should be is perfectly worthless.