Ability to organize issues in various ways, more powerful search and filtering capabilities, easier to track work done and plan work that needs to be done, etc.

Ability to organize issues in various ways, more powerful search and filtering capabilities, easier to track work done and plan work that needs to be done, etc. For a small project it's probably overkill, but when you need to manage a large number of tasks and/or a large number of workers (including product managers, QA, etc.) you need more than a simple text box with some labels.