Maybe these mythical good project managers exist, but I've never seen one. I wouldn't have the first clue how to hire one. So I'd rather do a bit of less pleasant non-engineering work than lose the whole company.
In 11 years I've only worked with two that I thought were great. But those two have convinced me that they can add a tremendous amount of value.
Think of them as oil in an engine. The best ones know how to communicate extremely well, are paragons of organization, and know how to facilitate decision making.
What was the background of the two great project managers you worked with? Had they always been project managers or did they transition from some other discipline?
I've found with project managers more than other positions, you get what you pay for. The best project managers command exorbitant fees because of their reliability, to the point where bringing them in can be counter productive. But if you have the cash, you can definitely attract top level talent.
The worst was the one who was an ex-programmer and would add ridiculous technical requirements to everything. We spent 1/4 of the time writing useful product features and 3/4 of the time working around those requirements.
But the best company I worked at eliminated project managers about halfway through my time there, not because they were bad per se but because they simply weren't contributing anything. Teams had good contact with clients so had an understanding of which features were wanted (the team lead did have to prioritize client feature requests, but that wasn't a whole lot of work or argument). Engineers were perfectly capable of allocating assignments with a reasonable balance of fun and not-fun (and honestly I don't see how a PM is supposed to save you time there, unless they know what everyone on the team likes and doesn't like). And written, rigid feature specs would only have slowed us down - developers were trusted to have a reasonable sense for what a feature needed to be.
At some companies, project managers have "responsibility" for projects but no authority or engineer time to direct. They get the projects that are too important to cancel, but not important enough that anyone with real authority in the business wants to spend time pushing for them.
