Why do I have to catalog my content again after reinstalling the software?
The software creates a catalog of all the files that it finds on your devices. It also stores "previews" which are high resolution images of files which allow you to see content even if the device is no longer plugged in. This catalog can become quite large and has no value if the software is uninstalled. For this reason, when the software is uninstalled, the catalog is deleted. If at a later time the software is installed again, the catalog has to be rebuilt.
Note that when there is a new version of the software and it is updated, the catalog is retained.