Product people are great for selecting which features to build out and which bugs to address, but are poorly equipped to decide how to prioritize things like: performance optimizations, bugfixes that haven't (yet) been reported by the end users, code refactoring, paying down tech debt, modernizing tooling, misc quality of life improvements for the engineering team, etc.
If the company pays me to close tickets and Jira stories, why should I care about improving its products?
If the company pays me to actually improve its products, then sure, I would do that.
If you force every little bug to go through the product manager, you take time away from the PM to do big picture things by forcing them to track every little thing that's broken, and create a lot of friction for even the littlest bug to be squashed. This fosters an eng culture of "not my problem," which leads to bugs slipping through the cracks for years.