[candybar]

You still need to aggregate and contextualize these in terms of overall business and product strategy. Yes, engineers can do that too and some percentage of engineers are good at this as well - and being able to understand and formulate product strategy can be an important part of an engineering leader's skill set - but that's not that common and ultimately you need some level of specialization and you can't run an org expecting everyone to be able to do everything.

I've done both Eng and Product and most engineers don't have sufficient understanding or appreciation for the importance of product strategy. It's also important to be able communicate strategy coherently at some scale, especially if execution isn't expected to be completely top-down. At some point, engineers just have too much else to do and you need coordination.

Edit: I'll also add that engineers aren't the only ones doing work - Product Managers are expected to be able to coordinate across functions and get everyone on the same page, not everything is about just providing input to engineers.