Because blocking the UI thread for any kind of I/O network, process, file, whatever is such a great thing. Or even just syntax highlighting, which actually prevents you from being able to move your cursor in vim sometimes.
Vim's source code is an abomination, and Neovim is making it unquestionably better.
A single-threaded UI means I can easily tell what Vim is doing at any time. It means the editor never feels clunky because indexing or some other background activity is hogging resources. It also means I never get a "process is running" prompt like in IntelliJ or Emacs when I want to exit.
No, instead you find that you can't :q - or type anything for that matter - because everything's frozen while vim is realising that the network drive is down, or you're waiting for the syntax highlighting to finish.