Par2 has inherent limitations that make it look distinctly historical (no Unicode etc.). There is a preliminary Par3, but the main reason why Par doesn't enjoy the popularity it should have is simple: Abysmal tooling.
I've tried all the usual implementations that are available on Windows recently, and they were all unusable. Like in "try to give it a hundred files, each in a single-megabyte range, and it will crash hard".
Why would par2 need to handle anything related to encoding? It's acting on the data independently of the actual contents of the data.
I'd agree about the tooling problems with it, it's "acceptable" on a linux/unix command line but I've never seen anything elsewhere that even looked halfway usable.
I've tried all the usual implementations that are available on Windows recently, and they were all unusable. Like in "try to give it a hundred files, each in a single-megabyte range, and it will crash hard".