Absolutely nothing.... but for some reason I find it interesting when people rewrite things that I didn't know needed rewrites. Sometimes these projects are doing someting really interesting. Grep is one such example, noone was saying that grep needed a replacement. In fact, it was used as a benchmark for regex (which is how rg started, to compare rust regex against grep), then someone creates rg that outperforms grep and is much nicer to use. That is also why I keep an eye on GitOxide, since nobody ever accused git of being slow, yet there are someone rewriting git with amazing performance improvements.