Why would it be important for a company to have an employee and managerial self service portal?

Why would it be important for a company to have an employee and managerial self service portal? How do these portals benefit an organization? What are the ROI and cost considerations when considering one of these platforms? What are some of the best practices in implementing self-service applications and what are also some of the common errors? Would you recommend one of these platforms at a current or previous employer? Why? Explain your answer by using material from our reading assignment this week.