In my experience, companies are not thrilled to leap from server OS to server OS for a few percent points of extra performance. And even if they want a new server there are such things as central management systems that may or may not have problems with this new version of DragonFly BSD.
It's usually more that IT is not thrilled rather than management.
But more seriously, DragonFly is
BSD even though it's now technically a fork. So it shouldn't be a cultural or paradigm shift for most IT departments with BSD or Unix experience. And I really can't imagine any good reason for not
running PostgreSQL (or MySQL or most any other non-Microsoft SQL database server) on anything other than a BSD core if a version is available for it. The cost savings can be significant. And BSD is as rock solid as an OS can get.
But maybe that's just me?