While a bit less common for home networks, monitoring is one of the key responsibilities of a systems administrator in the business world. A good sysadmin
should be aware of failures in the systems that they're responsible for before the end user notices the problems. In fact, they are often aware of issues before they occur, due to monitoring resources to detect bottlenecks before they trigger any service degradation.
Monitoring can fall into a number of categories, including graphing, alerting, and in some cases, automated fixes.