Comment by skybrian

I think you might be underestimating browser compatibility.

There are a lot of browser API's. They're portable, designed with security in mind (at least somewhat), usually well documented, reasonably easy to understand, and people already know them. So, even if it's not a browser, you may prefer JavaScript so you don't reinvent the relevant API's and there's less to learn.

Deno itself is a good example of this.