"We'll do both!" you announce with false confidence. "Discovery team runs workshops while development team starts building the architecture. Parallel tracks!"
Week 1: Seems efficient. Discovery is gathering requirements. Dev is building framework.
Week 2: Discovery learns the data structure needs to be completely different. Dev has already built the database schema.
Week 3: Discovery identifies new compliance requirements. Dev has to scrap two weeks of security implementation.
Week 4: Discovery discovers (ironically) that a critical third-party integration doesn't actually exist. Dev has built the entire connector module.
Week 5: The requirements are still changing. The code is constantly being refactored. Nothing is ever "done" because "done" keeps moving.
Week 8: Your team is exhausted. They're building, rebuilding, and re-rebuilding. Every day brings new requirements that invalidate yesterday's work.
The dev team starts calling discovery "the chaos team." Discovery calls dev "the team that doesn't listen."
Week 12: You're massively behind schedule. Nothing works properly because everything was built on shifting requirements.
The CEO asks what went wrong. You try to explain parallel discovery and development. They cut you off: "So nobody knew what they were building?"
Technically correct.