They may be wiling to pay for RHEL for some critical services, but there are a lot of things where a full RH sub doesn't make sense. Dev/test environments, non-critical services, web applications and applications with high parallelisation. You want to support as few OS variants as possible, so by using RH clones there this way you can have "can't tell by the taste" compatibility across all your systems. Plus it makes it easier hiring people.