By comparison, the system of tools around Attrs and Cattrs is a bit scattered and underdeveloped. I don't think there's a technical reason for it, that's just how it happened. It would be great to see either a competitive parallel "stack" developing, or increased interoperability from libraries that currently only support one or the other.
For this reason, in my personal projects I use Attrs almost all the time when writing new classes. I don't use Pydantic. But at work, we are very likely going to adopt the aforementioned "Pydantic CRUD stack" for new internal services, specifically because our needs are straightforward, and for straightforward use case is a "just works" and "there's only one right way to do it", which I think are extremely valuable features when operating in a team.