Because the assumption is code is expensive to generate. Otherwise why would you put all the upfront effort into all of the planning?Just write some code and iterate on where it goes.
Code being expensive would be one reason to plan, but hardly the only one. Some other reasons: cost of failure (don't leak customer PII), maintenance, unclear requirements, unclear success criteria.
Code being expensive would be one reason to plan, but hardly the only one. Some other reasons: cost of failure (don't leak customer PII), maintenance, unclear requirements, unclear success criteria.