I worked at a place with no product owner and I would literally have to task switch from writing code to talking to an irate customer on the phone because we only had basic tier 1 support. I would also have to fly out to the customer’s actual site to live debug while they stood over me mad. I’d have to also gather requirements and ideas from them. All while also needing to do a full-time software engineering job.

I would have killed for a Product Owner to shield me from that!