Because if they do something that requires changes to the Rust code, the Rust for Linux folks will take care of it for them. This has been explained repeatedly.
Now, if rust is only in a few corners of linux, then there isn’t much distinction between a linux C dev and a full linux dev, and it’s no big deal. But the goal appears to be to use it more extensively than that.
To me, the entire approach to this is backwards. Rather than trying to force a preconceived solution, turn it around and say to linux devs “Look, memory safety is an issue in linux. What can be done about it?” Let them determine the solution. That’s when you can make the case for rust. (Though you probably won’t be successful if you keep blowing off the concerns of linux devs.)