The effort to create a Service Level Management System is very significant. Organizations that have a system in place have higher customer and employee satisfaction ratings. After all, when every case is considered severity level one and every day is a fire drill, it is hard to enjoy your job for very long. That is why the turnover in support organizations where Service Management Systems are in place is lower than organizations where they are not. So, with higher customer and employee satisfaction, lower turnover, greater productivity and reduced cost, why would you not want to have a Service Management System guiding your organization?
Here is a great White Paper on Implementing Service Level Agreements. See https://www.givainc.com/white-papers/index.htm