Most people that are running Kodi are not using Emby. Kodi is good for local use but I don't think it has all the remote (being able to watch your movies when you are away from home) functionality that Emby has.
True but that not means Emby server is not useful for Kodi clients.
I know from first hand experience that Emby server is able to serve media very well to clients running Kodi with "Emby for kodi" addon even on WAN scenarios.
Yesterday a friend of mine was able to watch movies (up to 80 GB MKV sized movies) from my collection SMOOTHLY , the stream was using "direct play" mode in Emby server (no transcode, no container change).
You only need a good upload speed (+100 Mb) on server side and also a good download speed on client side (+100).
This was not local...I live in Spain and my friend is in UK. 