Gantt charts are used to plan projects using long term and short term deadlines. In my experience it is important to incorporate both of these components to the timeline. Often, only hard deadlines such as those determined by external factors are considered. In order to meet these crucial deadlines, smaller tasks that are key components of an important phase help break down the project visually.
Some people only use gantt charts as a checklist. This is limiting the visual benefits of using a Gantt chart. This happens more with larger, more complex projects. To avoid this, a subset of charts can be created. This can be grouped by date or by modular component.