Lots of companies try and impose things on their employees which a judge would obviously rule to be unlawful. Sometimes they just don’t think through it carefully; other times, it’s a calculated decision that few employees will care enough to actually get the issue in front of a judge in the first place. Especially relevant for something like a non disclosure agreement, where no judge is likely to have the opportunity to declare it unenforceable unless the company tries to enforce it on someone who fights back.