Actually, given that I'm in the process of installing my old library on a new home network, the main reason that I just want to update the library and nothing else, is that while I'm messing around with file locations, I keep ending up with huge numbers of files not found that I want to get rid of.
That said, that's also the reason I use it under normal circumstances - for some reason that I can't think of now, I always seem to have those red-x files lurking around that I need to purge.
However, whenever I'm doing an important backup, I want to do all those things that the import dialogue does, and the option of simple clicking on or off for which folders or drives are searched is great.
My main point is that it seems inconsistent to have a 'Library' menu under 'File', and then not have a link to all those library-specific things.