If you want to call ruff directly, this doesn't change anything. It's a purely optional feature.
However, to answer the question generally: people want this for the same reason that most people call `cargo fmt` instead of running rustfmt[1] directly: it's a better developer experience, particularly if you don't already think of code formatting as an XY-type problem ("I want to format my code, and now I have to discover a formatter" versus "I want to format my code, and my tool already has that").
However, to answer the question generally: people want this for the same reason that most people call `cargo fmt` instead of running rustfmt[1] directly: it's a better developer experience, particularly if you don't already think of code formatting as an XY-type problem ("I want to format my code, and now I have to discover a formatter" versus "I want to format my code, and my tool already has that").
[1]: https://github.com/rust-lang/rustfmt