There is no code in a running kernel written in Python, Perl or Ruby. Those languages are used in kernel’s source code tree in supporting tools, they aren’t kernel code.
“Even worse”? Are you saying Rust is bad?
Those are not “system languages.” Even without actually checking, I’m confident enough to assume that their presence in the kernel repository is as support scripts and such, not stuff that actually gets included in the kernel when it’s compiled.
Edited for better clarify on systems languages.
They aren’t “languages for OS” either. They’re scripting languages, and they’re being used for scripts. In other words, they’re there because they aren’t worse and in fact are the right tool for the job.
The kernel is written in C and a bit of assembly. When support for a new language is added, that’s big news and worthy of headlines. The other languages are just there for various tools and helper scripts and are not used for kernel code, so not newsworthy by any means.