Predictable release cycle is already worth it for server use and also for those who need commercial support.
And zfs is too good to miss and Ubuntu has supported it for very easy use for quite a while.
And it feels comfortable to use a distro who has corporate customers as they may lose substantial money if they're not careful.
Now speaking of corporate customers, well that is not a great argument, as even more users use Red Hat, which is IMO an inferior distro.
What is good about Debian, however there is a very little chance of it disappearing one day, or dramatically switching to snap-only or some other nonsense deviation. In a way, it is even safer for corporate use than Ubuntu. This is why it is used in Google (the used to run Ubuntu before on their workstations).