[kirso]

How is it difficult? Each product has a metric / OKRs behind it and if it doesn't then something is really really wrong.

Can hardly see an argument of everyone pivoting based on loudness and charisma. People would usually fail here on analytics, design or even technical questions of data flows.

[alphazard]

Product quality is difficult to measure. Even if it was easy to measure (as you seem to claim), it's difficult to know if a improvement in metrics is attributable to the product manager or some other factor. There are a lot of forces driving product evolution.

Contrast that to metrics around demand generation. If you have a sales team, they can work "how did you hear about us" into the conversation. Maybe you are tracking where redirects to the website come from. It's much easier for a marketer to prove that 100 prospects got in touch as a result of something they did, than for a product manager to prove the product is better because of them.