Companies are stepping up efforts to help employees get academic degrees. So why aren’t more employees taking advantage?  McDonald’s Corp. recently announced it would expand the eligibility requirements for its tuition-assistance program. Walmart Inc., Yum Brands Inc.’s Taco Bell, Kroger Co. , meanwhile, all have announced new tuition-assistance programs in recent months. The trend reflects efforts to attract and retain workers in a competitive labor market and to help them meet the changing demands of their jobs, says Jaime Fall, the director of UpSkill America at the Aspen Institute.