Kubernetes is simple enough to setup yourself. They have well documented tooling, and a solid do it yourself guide. OpenStack has none of that (that I can find). You select RedHat Openstack (RDO) or Canonical OpenStack (MAAS), and you have to use their all-in-one system to have a deployment- and that requires a narrow set of variables which every environment might not have. Which is insane- and will hinder adoption.
EDIT. Not 100% correct, see below comments.