Apples and oranges. Corporations that feel they need Enterprise Support, either for the OS itself, or for software that runs on the OS (commercial databases, engineering tools, etc.), pay for Red Hat Enterprise Linux. Or, if they were small just feeling like throwing caution to the wind, they would use Centos (and not tell anyone that it wasn't actually Red Hat). These are businesses and software that used to run only on commercial UNIX operating systems.

People tried selling Enterprise Support for Debian back even before Red Hat went commercial, if I remember correctly, but somehow Red Hat timed their effort right and became the defacto replacement for UNIX in these environments.