They have so far. What would you propose they do? Wouldn't that be completely contrary to the philosophies you are so enthusiastically supporting on this forum? Of course it would. Apparently you haven't even fully thought out your position, or actually understand what is happening in reality.
Which, I don't think will be very much because just look at how popular RHEL is, and how many people are using WhiteBox and CentOS.
Further, I'm not advocating they do, I'm just saying they technically can if their legal counsel decided to take action. With the rate of tech companies, I'm inclined to think they'd pull the GPL'ed source and then attempt to sue distro makers for lost profits. However, their attempt to recover those profits will under a functioning court system fail because Red Hat allowed the public to use their source under the GPL, which is a rather loose license.
But, I personally think there's two things going on: a.) there's some understanding that the distro makers aren't supposed to just simply build up a CD from the RH sources--they need to differentiate it, and b.) it's rather unlikely RH is posting the complete source in a ready-to-use format.
End result, they're likely to be unsuccessful in such an endeavor.
That said, the GPL is unique in that v.2 doesn't explicitly outlaw selling copies of your program so long as the program is freely available either as source or as a functional version. So, I could build my own distro as in post 45--dl the RH source, make some tweaks, make the source available on my website, and then sell the copies at school.
That's what I think is going on here. There's differentiation from the raw RH source and the RHEL production version, and the GPL criteria are being met. No big deal.