Places vs. Places . . Why the differences?

[Young]

I'm just curious.

In both Places from the main menu, or Places in Computer/Nautilus,
my NTFS partitions show up just fine. They're mounted in /media and usable.

However, they don't show up in Places under the Change Desktop 
Background / Appearance Preferences > Background, then +Add Wallpaper.

In fact each of these Places has its own unique list. Is this 
inconsistency on purpose and with a good reason, or just the way it is?

(They are reachable by File System / Media, and even easier with the 
links to my photo directories I dropped into the Pictures directory 
under Home, which is at least one way to make the Pictures directory 
usable.)