These are great points, if you already have Ruby in your stack. For me, when Bash ain't enough I upgrade to the Project language (PHP, Python, JS, etc). For compiled project I reach for LSB language (Perl, Python) before introducing a new dependency.
Ruby is fantastic for the main project language, too! And is also standard on many Linux distros.
In my professional experience on medium to large-sized projects, its lack of explicit typing, the habit of Rubyists to use its fairly-substantial metaprogramming capabilities at the drop of a hat, and (for projects that include pieces or all of Rails) the system's implicit library loading make such projects a nightmare to reason about and maintain.
I'm sure these aspects are manageable with a small group, or a very, very disciplined group, but when you have large-sized projects that have been continually worked on for ten, fifteen, more years, you're just not going to be able to guarantee that everyone involved will have the combination of knowledge and discipline require to ensure the thing remains easy to understand, extend, and maintain.