Every product team needs product management, but not all product teams need a dedicated product manager.
A somewhat lose analogy is a football coach. You don't need a coach to play a casual game, but you'll want one to play leagues.
An early stage startup without a founding PM can do product management themselves, but at some point, they will need a dedicated PM to take over.
Why? The best answer is from Jack Dorsey, one of the greatest product managers of our time, who calls product managers as product "editors".
“There are a thousand things we could be doing, but there's only one or two that are important. And all of these ideas and stories from engineers, designers, support people are going to constantly flood on what we should be doing. And we really need to pick the one or two that are doing drive and sustain the network and the service and the product. As an editor my job is to chose those one or two things that make sense”
