Who writes user stories on your team?

Depending on the team structure, product, and the nature of the work, the role that does the work of authoring user stories seems to vary a lot from company to company and team to team.

I have personally worked in companies where the product manager writes the vast majority of user stories, but I've also worked in organizations where software engineers are typically responsible for writing their own user stories. In other teams that I've worked with, there is a dedicated product owner or delivery lead who authors most of this content.

What do you do in the teams that you work in? How important do you see this practice for the success of the team and ultimately the success of the product?

Part of the reason I ask... I'm building a product called kojito.ai that helps product teams write better user stories faster. As a PM would you be interested in using a tool like this yourself, or would you prefer to enable other parts of your team with something like this?