Fair question, you shouldn't be getting downvoted for it imo.
Larger projects need a way to collect bug reports, feature requests, maintain documentation, and set up milestones and release schedules, at a minimum. Ideally you want all of this integrated into your vcs, so that when a developer decides to push a commit related to a specific bug or feature request, that commit gets attached to that bug or feature request.
When these are set up and run well, they are very powerful for mid-to-larger organizations.
Larger projects need a way to collect bug reports, feature requests, maintain documentation, and set up milestones and release schedules, at a minimum. Ideally you want all of this integrated into your vcs, so that when a developer decides to push a commit related to a specific bug or feature request, that commit gets attached to that bug or feature request.
When these are set up and run well, they are very powerful for mid-to-larger organizations.