I figure over the next year or two when new versions of these packages come out I will be able to adopt them more quickly and easier than if I had to wait on an RPM. And in the case of systems that are getting old the rpms may never arrive.
On the contrary, many upstream developers are adding spec files to their tarballs so you can build from source and have an RPM at the end to install. Unless I know the repository well, I tend to grab 3rd party stuff either as a tarball with specfile or a source RPM and rebuild it.
