Professional applications (e.g. CAD,…) generally don’t support many distributions. In my field, RHEL and SLES are widely supported and a few tools also support Ubuntu.

We’ve got over two hundred Rocky/Centos vms. all of them ‘pets’ that would require manual migration of lots of very different services, many of them bespoke. That’s quite a lot of work.

Thanks for the answers I learnt something new :)

Switching is not always trivial.

I have a huge build that only works on EL7. It will take months of focused effort to unfuck that build code.

RHEL gets enterprise support from RedHat / IBM.

Point is, if you work for some big corp, when you buy something, you want proper warranties meaning people to blame if it breaks down. I have seen corps want to pay for stuff available free just so they can point at someone if there’s a problem. Ubuntu is mostly fine, Canonical does offer support, but “nobody ever got fired for choosing IBM”.