While I think that ought to be a requirement for getting a CS degree, not all universities do. Moreover, being able to code isn't a boolean - while some people

While I think that ought to be a requirement for getting a CS degree, not all universities do. Moreover, being able to code isn't a boolean - while some people are indeed totally incompetent, among the competent people, some are better than others, and some have strengths and weaknesses that would make them more ore less suited to a particular role. It behooves an employer to try to measure these things.