RPM/yum has grown up a lot, and yes -- it works as well or better than apt-get at basically everything now (openSUSE's zypper is actually spiffier still). But for a long time Debian and its derivatives had an overwhelmingly better package management experience, and a much larger universe of packages to draw on than the RPM distros did. And this intuition persists in the community.
Though I will say this: for all the feature and usability improvements we've seen in yum, the Fedora people seem to be trying their damndest to break them all by this insane wrapping in "PackageKit" that manages to succeed in both dumbing it down to the level of unusability and "enhancing" the power user experience by spending 3-5 seconds every time you typo a command trying to figure out how to install "mkdri".
FWIW, Ubuntu has it's own "waste time everytime you typo a command" functionality, at least in the release I'm on. It's actually useful every once in a blue moon...
Though I will say this: for all the feature and usability improvements we've seen in yum, the Fedora people seem to be trying their damndest to break them all by this insane wrapping in "PackageKit" that manages to succeed in both dumbing it down to the level of unusability and "enhancing" the power user experience by spending 3-5 seconds every time you typo a command trying to figure out how to install "mkdri".