This, a thousand times. I'm on CentOS 6 and have switched to docker for some services that don't easily run on that OS. However, I found out the hard way that docker isn't supported on CentOS 6, by having some crashes when building containers (due to bugs in devicemapper). Painful.

I really wish RH had found the time to fix RHEL 6 and support docker.

RHEL 7/CentOS 7 is a big step for many. RHEL 6 isn't even near EOL and many people (including myself) wanted to get more mileage out of CentOS 6.