Why is user testing crucial during the product design process?

User testing is essential during the product design process because it allows designers to gather real-world insights about how the product performs in practical use and how users interact with it. By observing actual users as they engage with the product, designers can identify functionality issues, uncover pain points, and gather feedback on the overall user experience. This firsthand information is invaluable, as it guides iterative improvements, ensuring the final product meets user needs effectively.

The other choices, while relevant in different contexts, do not capture the primary importance of user testing. Finalizing the budget for development, establishing brand identity, and meeting regulatory requirements address other aspects of product development but do not focus on understanding user needs and experiences, which is the core purpose of user testing.