It's a bit more useful, but the breakage has to be seriously impacting my use of the system to roll my own kernel outside of the distro's packaging (the only one I've done is manually applying a fix to a Gentoo kernel and even then I just throw the patch on after the normal stuff).
I don't see why. Users can manually update their kernels in this case. I don't believe that's an option you'll get with a proprietary OS.