I know why they use RHEL - support is apparently good and not every corpo wants to keep some linux experts on payroll to fix the rare issues that need a bit more expertise. And they keep old versiond of Red Hat updated for longer so you old crusty enterprise garbage can stay garbage few years longer and claim "but OS is updated" in audit.
I have no idea who in their right mind would use derivative, it has zero benefits and is just build worse than vanilla Debian.