Conventions of politeness aren’t based purely or even primarily on functional considerations—putting one’s elbow on the table doesn’t affect the taste of the food—and they are apt to become tools in the hands of pretentious fools. Yet the proposition that they should therefore be done away with is manifestly preposterous. Certain conventions will govern the ingesting of food in a civilized society. Humans abide by customs when they wish to please their companions or ingratiate themselves, and there’s no point in trying to convince them to stop.
So it is with the prescriptivist temperament in language. The employer will always want to know whether a job applicant can write and speak the way educated people write and speak, considerations of clarity notwithstanding. The ambitious student will always take secret pleasure in saying “It was she” instead of “It was her.” The conscientious parent will always encourage his children to mind their grammar, and partisans of various stripes will always cackle when disfavored politicians fall afoul of the rules (“The goals of this country is to enhance prosperity and peace,” “Give Al Gore and I a chance”). Descriptivists like to think of themselves as clear-eyed realists. But it’s they, and not the sentimental traditionalists, who wonder why we can’t dispense with all these arbitrary “rules” and just get along. Is there a dream more fanciful?