Storing Bookmark (of audio/video file position) in the media device than media player:
While playing media files, bookmarks are stored in the player (such as CD player) for the reason media is read only type. This is good strategy for readonly media types. But this is not necessarily best option for Read/Write media files.
If we change pen drive across multiple players (say car MP3 player and home MP3 player), bookmarks are not carried with. If we save bookmark in pendrive, we can resume playing the media in another mp3 player.