Since Docker Swarm is a native Docker tool, it exposes the Docker API, making it possible to integrate it and communicate with other Docker tools (CLI, Compose, Krane, etc.).

This also means that containers can be launched with a simple docker run command and Swarm will take care of the rest, such as selecting the appropriate host on which to run the container.

This gives you a well-rounded workflow.

Docker Swarm is open source and provides great guides/documentation for those who want to contribute.

Docker Swarm is much more lightweight than alternatives: Kubernetes and Mesosphere. Kubernetes, for instance, is very complex - it downloads and installs half of the web, where Docker Swarm has much, much smaller footprint.