You know the saying have two ears and one mouth? Where are your ears? If you’re solely focused on listening to your external market, you’re missing out on making a key internal deliverable, and ultimately your product, the best it can be.
Knowing the base functionality that currently exists for a product is the first step in gaining necessary context to grasp what gets added on next. For organizations with established and expansive product portfolios, current functionality can be an area of contention between product owners, requirements writers and consumers of requirements.