It's true that they guide priorities toward the need of the business but it's also true that they don't. There's empire building, favors and horse trading to be

It's true that they guide priorities toward the need of the business but it's also true that they don't. There's empire building, favors and horse trading to be done between managers. There's also battles to be waged for territory. And while I do agree that's important to learn how to frame things in terms of the business benefit there are going to be things that aren't as simple to translate into a straightforward benefit and KPIs. If you're working on something that just increases developer happiness to help with things like general productivity and retention measuring the benefit for any one thing isn't always going to be feasible.