1) Code sharing between backend and frontend is very useful sometimes. 2) JS is "trusted" in more places (or at least considered far more easily "sandboxable")

1) Code sharing between backend and frontend is very useful sometimes. 2) JS is "trusted" in more places (or at least considered far more easily "sandboxable"). There are several large "serverless" or "cloud-native" hosts that will let you run all the JS you want at large scale, but have far more hoops to deploy/run other languages, and sometimes if they do support it they support only when compiled to WASM.