I go for the latter but hypothetically:

- Easy access to (newer versions of) some particular package like a device driver in distro repos[0]

- You prefer the Kubuntu default experience more and don't want to customize

- Company policy

[0]: For most packages, ~half the time Debian stable is ahead of Ubuntu LTS as the former is the base of the latter. Currently latest Ubuntu LTS 24.04 is still based on Debian oldstable. It will catch up with 26.04, until next Debian stable release. Sometimes, though, Ubuntu do their own backports or releases where Debian stable does not.

I migrated my home machine from Debian to Kubuntu a few years ago, I don't remember why )) I think that it had something to do with the installer.