The token system is an important part of Drupal because it allows us to easily transform raw data into useful values using placeholder strings. It is a widely used and flexible system that many contributed modules build (and will build) upon. The great thing about tokens is the UI component. There are modules that will allow users to define strings in the UI but make it possible to fill it up with various tokens that it will replace. Also, this is something you can do as a module developer.