Why would they be rarely used? That's a very common task. A quick search on GitHub shows lots of likely uses: https://github.com/search?q=number_to_currency+in

Why would they be rarely used? That's a very common task. A quick search on GitHub shows lots of likely uses: https://github.com/search?q=number_to_currency+in%3Afile+language%3Aruby&type=Code&ref=searchresults https://github.com/search?q=number_to_currency+in%3Afile+lan... https://github.com/search?q=number_to_human+in%3Afile+language%3Aruby&type=Code&ref=searchresults https://github.com/search?q=number_to_human+in%3Afile+langua... https://github.com/search?q=number_to_percentage+in%3Afile+language%3Aruby&type=Code&ref=searchresults https://github.com/search?q=number_to_percentage+in%3Afile+l...