Mindshare is important here, because otherwise, something like RedHat would likely be the default choice for businesses.
I mean, with regards to Linux Enterprise stuff... it is. SuSE is the boss when it comes to SAP, but otherwise everything lives on some flavor of Red Hat or derivative; CentOS is everywhere.
In the Enterprise we only roll with stuff that is officially supported. Hiring freezes, layoffs, and general work ebb-and-flow means we will need to rope in help at some point, and while I may be a wiz at some CLI functions I'm not up on what each patch is doing to the environment. Having a support contract to lean on is a huge advantage.
Canonical was (is?) effectively trying to do this on the .deb side of the house (as opposed to the .rpm side), though I don't know how successful they were/are. I looked at interviewing w/ Canonical, but the Glassdoor reviews painted a picture of an org that was having deep growing pains and internal struggles.