This is the time of year when many companies are asking workers to fill out surveys that measure how content they are with their jobs, compensation, benefits and managers.HR departments often find it difficult to get employees to complete these employee engagement surveys. Sometimes, when workers do fill them out and HR discovers a department has a morale problem, it can be just as difficult to get those workers to speak up and explain why they're unhappy.And there's a reason for that, employee engagement experts say.