It totally depends on your teams workflow on how your branches relate to your workflow and release strategy. Let me give 2 different examples of where you would want an integration branch, and where you might not.
Example #1
You have 5 Feature Branches, some or all of them will be integrated together to create the next release. In this case you clearly want an integration branch.
Example #2
You have 3 branches representing v1 - v3 of the software that are all under development simultaneously. In this case you might not need an integration branch. All v1 code should be merged into v2/v3 branches, but not the other way around.