To the extent that the question has any utility at all (see gwadej's reply) that is not a problem. papidave's replyhits pretty close to why: when you are selecting a candidate for a position a base level of competency is assumed. You've got to have someone actually capable of doing the job. If the question provides any useful information, that information is related to finding the most appropriate candidate, not for making the cut between immediate rejection and further consideration.