The first principles of DevOps - Principles of Flow - mandate to make all flows (processes, partial Value Streams) within an organization visible. Within DevOps Organizations, the work flows from development to operations. From customer request to production. From left to right.
Only when the work and flow is visible, all Work in Progress can be identified, analyzed and subsequently addressed. Kanban boards are a tool that help to visualize work in situations where it otherwise may not be visible (e.g. software development).
Applying this principle results in transparency of the flows in all pipelines. This allows for optimization of all pipelines globally. This in turn allows for fast flow of all (independent, local) tasks.