Support for Elasticsearch is not an advertised feature of our plugin. At this time, it is not well supported by hosting companies, and where it is supported the setup is not at all easy.
I tried to install it on my own server with Cloudways and failed, and I am reasonably competent with installing my own custom server stack as well. Now that I use a host to do such things, and Cloudways are quite good at support, they admitted it was hard to setup and needs a lot more work before it is usable.
IF it becomes well supported (which would require hosting companies figuring out how to make it a quick one click install for their server stacks), then it might gain traction with WordPress site developers. At this time, the ElasticPress plugin has only just over 2000 active installs, most of which are development installs.