Product owner/manager often works out fine as an informal position, where certain people in leadership roles are making decisions because they have an excellent aptitude for doing such; they especially have the ability to understand and empathize with their user base.

That works fine until it stops working, and then it works horribly, because engineers have asserted themselves as antagonistic product owners: I know what customers want! And they just plain don't. Things can go completely insane. It boggles my mind how badly some otherwise competent folks can botch this.

I didn't even realize how important this role was until I was working with people who clearly had no business asserting themselves into it, and I'd rather have someone less technical doing it than an engineer who is awful at it.