I do it first and foremost because I dislike the error checking story in Go, and writing Rust for web stuff doesn't really feel too dissimilar to hacking on web frameworks of years past. In fact, I'd argue that web domain stuff is where Rust is relatively mature.

But this all said, there's definitely a point to be made here - Go works fine for so many use-cases, people should use it if they like it or it fits the story better. The idea of "one true language" has never worked out.