[Isamu]

>lack of knowledge hoarding, healthier knowledge transfer and decision making, and reduced waste.

This. It is so much more efficient as an engineer to have a clear idea of the values and needs of the users, and to share a clear vision with the pm of where the product should be going.

That said, at most places there is an almost total lack of appreciation for the amount of engineering and planning and effort that goes into providing a competent, professional product when those tasks are not directly providing customer-facing features. But it's part of the engineer's job to educate the pm as well about unappreciated realities.