Currently on OS X, the wallet.dat file is in the same location as the blk*.dat and files. This means that if you want to back up the folder wallet.dat is in, you are backing up multiple large files that change regularly, resulting in longer backup times. While you can exclude individual .dat files, new ones are created regularly, making this a manual task (and a pain).
If either the Block files were moved into their own directory, a user could exclude the folder with the Block files from a backup routine (such as Time Machine), making the backup process faster and more efficient. (Since the files can always be regenerated on the fly, they are not as critical to back up as the wallet.dat file is.)
