The initial Toaster designs, waaaay, way back in time, asked for the 'Dependencies' and 'Reverse dependencies' columns to be sortable. The idea was that knowing which packages were the most dependency heavy, or which ones have no dependencies at all, could be somehow useful. 

At the time, it was too much effort to make those columns sortable, so we dropped the functionality. However, it has come back in connection with image customisation. Sorting the list of packages included in your custom image by their number of reverse dependencies might help you find 'orphan' packages that can be removed. 

Maybe it's time to put the effort into making those dependency columns sortable.