Every software release ages in months; every workflow is older than the software running it. That asymmetry is a hint about where to start.
The workflow is the specification
A workflow map that includes inputs, actions, decisions, exceptions, outputs and human responsibilities is effectively a specification for the integration. It tells you where automation is needed, where rules are mechanical, and where judgement must stay human.
Without it, you are guessing — and guessing is expensive when the system later has to survive production.
Where projects fail
The common failure is integration, not software quality. A system that cannot reach the CRM, cannot read the documents, and cannot write into the production tool is a demo. Workflow mapping is how you discover those requirements while they are still cheap to solve.