I'd say there are two (positive) reasons to it, since it only really appears for newer languages that are just gaining popularity 1. An improved tool was made,

I'd say there are two (positive) reasons to it, since it only really appears for newer languages that are just gaining popularity 1. An improved tool was made, and presumably was made easier by the language somehow. 2. The tool serves as example of larger product written in that language Both facilitate further usage of the language (by evangelism), show the language as being up-to-snuff (production-viable), and the existence of this codebase acts as an example for others within that language community. It's not so much the language makes this tool better, but for that particular community, that the language was used is important, possibly more so than the tool itself.