My assumption is it's for reducing the number of things they need to configure, and therefore troubleshoot.

It's easy to say "The newest Kali release is the distro the org will use" instead of "Use whatever Linux flavor you want and here's an install script that may or may not work or break depending on your distro and/or distro's version".

Them spending time troubleshooting a setup that's out-of-spec is still time billed, so it's better for their customers for everything to roll smoothly too. They also just want to execute their job well, not spend time debugging script / build issues.

From my experience, it is obviously not all the packages in Kali Repo will be in Ubuntu (or other regular distro) Repl. Lots of specific pentesting tool can be installed with just `apt install ...` in Kali, which make it a lot more convenient when you need to do pentesting.

Out of the box experience and some extra scripts :-)

Think about all the time saved not having to do sudo or su.

They don't know how to use Linux they just know Kali