Creating branches in git basically free and is easy to do. This has lead to the development of techniques like git flow and other branch related work streams, which are now commonplace in development.
If you have a project being worked on by many developers you can get into the situation where there are many branches in the project. Some will be merged, some will be worked on currently and some more will be branches that were worked on, but never finished (for one reason or another). This can lead to some confusion over what branches are being worked on, especially if you want an oversight on the current health of the project.