I understand the concept, though: Back in the day, you'd port a server to a platform and you'd feel good about yourself until the next major release of the software; bugs and security issues be damned. Today people expect a recent version, at the very least quick back-porting of security fixes, and so on, and that's before you get to the wrapping layer that hopefully makes it all feel as though you're managing an Apple product rather than a usually pretty complex entanglement of various software.
Medium business and up will already have Linux or Windows competence enough to run all of these services in their native environments, so Apple is really only "losing" small businesses and home users here, and those were paying peanuts for a growing amount of responsibility on Apple's part.
Maybe Apple realized they couldn't compete in this space? Even so, support of macOS Server could have offered them long term benefits especially in the enterprise market.
On the other hand this could be an indication that they have been working on their own server software rebuilt from the ground up using Swift and the latest macOS APIs.