Being the desktop Linux support person (as in, no computer support from me unless it's Linux) for various relatives, I can agree with what you say. However, intentionally slow-moving distros like CentOS have one disadvantage on the desktop: what happens when new hardware comes along? It sometimes does. The user would be perfectly happy with the existing Linux version, but the new computer won't run it. Or an interesting USB peripheral is not supported in the kernel it is running, but would work in the much newer kernel of a bleeding-edge distro. This is where the lack of stable binary driver interface in Linux is a disadvantage.