Earlier quoted context omitted.
Get a piece of paper out and draw a bunch of circles on the left, and a bunch of circles on the right. This is your business team and development team respectively. Now draw lines between all the circles. Those are your lines of communication without a PM. This is a sad diagram, no one knows the whole story. Now repeat the exercise but draw an additional circle in the middle of the page. This time, the lines on the l…
This is a good point of view. Depending on your team or your org as a whole, it may be that you can manage communications just fine without one, but most of the time you can't. Also, in my org at least, the PM's main job is watching the budget.
In the example, every one of those lines consumes resources: time, context switching, misunderstanding, synchronization with the rest of the team.
A quality PM funnels all those lines through themselves. Their value is proportional to their ability to (a) bidirectionally extract, transform, and deliver useful information to both sides (developers and end users), (b) offload processing tasks that neither side is good at (merging similar requests, clarifying ambiguous requests, tracking down answers / requests for external teams), & (c) keeping a 10,000 view and coordinating tactical requests to align with strategic vision.
I like the CDC 6600's peripheral processors ( https://en.wikipedia.org/wiki/CDC_6600#Peripheral_Processors... ) as a computer hardware metaphor.