Maybe the main driver is that self-hosting of Elastic seems to be a very frustrating experience since it easily consumes a lot of memory and the default install seems quite insecure. Still AWS of course has automated all this. I guess completely free projects that are also controlled openly like Postgres don't have these problems and some of core developers seem to do lucrative consulting work. (So individuals are much better off I guess, and there is not the pressure to be like a Startup)