RHEL is the core IT/SysAdmin crowd. Anyone looking to get into this career space gets a copy of The Linux Bible and runs Fedora to get started. A lot of the Linux core functionality comes from, and is maintained by RH. This is not just a desktop choice for users. If you really want to get to a kernel hacking type of understanding of Linux RHEL documentation is a great baseline where there is info that does not exist in any other source except reading the source code.