Marketing of any kind. PMs often are either directly involved with marketing or work with a PMM.
Market and competitor analysis.
Tracking and being held accountable for KPIs, particularly P&L.
Strategic partnership development and management.
Corporate strategic planning.
Facilitating communication between sales and marketing, engineering, technical communications, and senior management.
I'm sure the list goes on.
And BTW, how it's defined varies from company to company. Some folks might place some or all of those responsibilities under the auspices of a CTO or COO.
So I disagree. I actually think the role is incredibly ill-defined... everyone has a different idea of what it means. Some people think it's basically an Agile Product Owner, polling customers, writing user stories, managing backlogs and working with engineers. Others describe it as "CEO of the Product", which implies a VP-level leadership-style position. Yet others probably see some weird amalgam.
And that's just what the role is supposedly defined as. I'll bet there's a wide gap between what a PM job description says someone should do, and what they actually do in practice when you have to marry the theory with organizational reality. After all, aside from various KPIs, I'm not aware of any obvious way to actually evaluate the performance of a PM...
And we haven't even delved into the ambiguity of moving from "what" a PM does to "how".
No battle plan survives first contact with Engineering, Marketing, Sales, Manufacturing, Finance, or Upper Management.
No battle plan survives second contact either.
A software product is defined by its set of features, therefore a product manager's job should be to manage the feature set.
Yes these tasks add value, but that doesn't necessarily mean they are, or should be, part of the Product Manager's job description. They may get done by Product Managers in some cases, but they could also be done by people in various other roles.