It is in fact very very useful but underutilized, for a very specific purpose - serving very large amounts of data from pretty much any runtime (like Ruby or Py

It is in fact very very useful but underutilized, for a very specific purpose - serving very large amounts of data from pretty much any runtime (like Ruby or Python). With those runtimes it works great because you can avoid stuffing the contents of the files you send out into the VM memory, greatly reducing memory and GC pressure. You can also cache the computation product in files, and then send those files out via sendfile() - and the computation can happen on a background thread or in a parallel process.