Why is a product designer not an interface designer? First of all, they should solve the task of the product, not the tasks of the user. Of course, a more convenient app is better for the business. However, when you designing an interface, it is always necessary to look back at the main business task and it is desirable to roughly understand the cost of developing and implementing a particular features. Thus, instead of the user standing in the center, a triangle arises: product-owner - user - developers, working within which the product designer must find optimal solutions and a delicate balance. I'll show how it works using specific examples from my own practice.