Product Management is a hard job. You need to be technical enough to understand whats happening and have a bullshit detector, but high EQ enough to speak human. The dumb ones become sort-of project managers, tracking another set of books for tasks. The smart ones tend to deeply understand the business and move up or out. It's also a tough role to govern in that sometimes they get alot of credit for the work of others, or get no credit for anything and languish from a career pov.

When this role is dumped into engineering, engineering management or general management, it weakens the engineering practice. If I need engineers, I need to select for that ability and frankly shield them from people on the outside. If the org requires that my teams handle interaction, now I'm hiring people with mixed skillsets in one org, which inevitably waters down the engineering side.