Yeah one of the major points towards vim is pretty much every unix environment has vim installed.
But yeah, that is why even I as Emacs user always bothered to at least know my way around vi, usually Emacs is most likely not installed.
Let's be honest: out of 10000000000's of SSH connections in a given 24 hours span, how many are to a "classical proprietary UNIX server"? 0.0001% maybe ? Is it really a use case worth optimizing for ? They should be treated as applicances, not as general-purpose computers.