I can't answer either of these very well myself, (although for #1 I speculate that it's prototypical nature makes it easier to target than a class-based language might be), but I think it's primarily targeted by language experimenters because it's incredibly ubiquitous and easy to demo to others (there's nothing new to install) and the coming generation of JS engines are finally using a lot of cutting edge techniques to drastically improve performance which should make their work more practical in the near future.