CentOS Linux release 7.5.1804 (Core)
When installed on other packages, users and groups were always created as needed, for example:
[root@cloud ~]# yum install VirtualBox-5.1
Running transaction Installing : VirtualBox-5.1-5.1.38_122592_el7-1.x86_64
1/1Creating group 'vboxusers'. VM users must be member of that group!
But on this machine, users and groups are not created. And not only when installing this package, but also when installing other packages where users should be created.