If you define an enterprise shop to mean a company that doesn't use software like ubuntu-server, congratulations, you are right, but you have also made a completely meaningless observation.
Well good thing that I didn't define it tautologically like that then.
Instead, I suggested - as did your parent comment - that support contracts are very important to "enterprise" shops. That can be considered a defining characteristic in so much as nebulous terms have defining characteristics. And if you don't understand the importance of those support contracts, a lot of their behaviour will appear strange.
It's simply a fact that a lot of these companies officially support RedHat, often Suse, sometimes CentOS, but rarely so far for Ubuntu Server. That may change, but Ubuntu is definitely not there yet.
Support isn't just about SLA's, its about your vendor actually providing software/drivers/etc for your environment. I think you will find many commercial applications only support recent versions of RHEL, SLES or in some industries Oracle Linux.
These products don't ship with source code, and they tend to fail spectacularly when put on machines that don't happen to have the "right" kernel, library and system tools. Frankly, having shipped binary products on linux in the past, it can be a real PITA just maintaining an application over three or four versions of RHEL or SLES (which have a lot more in common with each other than they do with debian based distros).
