Ubiquitousness is certainly a major selling point. The GNU coreutils are everywhere. I've made my peace with bash and make because I know they're always gonna be there.

This doesn't mean there's no value in developing one's own tools. Contributing to other projects can be quite difficult and time consuning. GNU projects are even more so.

We shouldn't limit ourselves to POSIX stuff either. Better software and tools can and should be built. Every attempt is valuable. And who knows? It might just turn into a staple of Linux distributions some day.