Adding a command in a Salt state is used when you want to have a command that is run after provisioning a server, run every time Salt manages the state of the system or run when certain conditions are true.
Systems Administration is changing, with the huge scale of internet company deployments and the popularity of cloud computing. Server deployments are often scaling faster than the systems administration teams supporting them. In order to meet the demand those teams are finding themselves changing the ways they have traditionally managed servers.