I've never seen Ubuntu used in a large enterprise. Redhat dominates the server market. They offer better certification, support, and a package repository geared towards stability and backporting. The seperate Fedora (new a shiny) from RHEL (old and stable).
Ubuntu doesn't really have that distinction. Shuttleworth is also kind of a character, and it's hard to rely on him keeping Ubuntu fixed on a particular use case. It's been desktop, then mobile/desktop convergence, and now containers and Kuberentes. Think startup vs big business.
Ubuntu is the default base image for Cloud Foundry, so in fact it's pretty widely embedded in enterprise at this point. But it's an implementation detail, rather than a separate line item on the invoice.
Google originally used Red Hat Linux (not RHEL) but migrated to Debian. They are using a custom version of all their stuff so its probably not really even Debian at this point.
Ubuntu doesn't really have that distinction. Shuttleworth is also kind of a character, and it's hard to rely on him keeping Ubuntu fixed on a particular use case. It's been desktop, then mobile/desktop convergence, and now containers and Kuberentes. Think startup vs big business.