>With that said, as a user of a tool/library/service, why should I care what language it's written in?
Because it tells you a lot with what other ecosystems is compatible, how much of a fuss it would be to interface with it (in case it's a library and you use e.g. Java, you'd normally prefer a pure-Java implementation instead of a C+JNI one, etc), if it's a good fit for your existing dependency management, if you know the language to go in and fix an issue or adapt it, etc.
It would therefore also be useful to state the platforms it would work on - in this case it seems to require a block-level device and is unlikely to be usable on Windows.
Because it tells you a lot with what other ecosystems is compatible, how much of a fuss it would be to interface with it (in case it's a library and you use e.g. Java, you'd normally prefer a pure-Java implementation instead of a C+JNI one, etc), if it's a good fit for your existing dependency management, if you know the language to go in and fix an issue or adapt it, etc.