I've noticed that players differ on some disks whether the subtitles default to on or off. For example, on my Panasonic F61A, any Alias DVD will start playing with the subtitles on, while my Pioneer will start with subtitles off. The Panasonic will only do this for some DVDs, not all of them, and there doesn't seem to be anything in its menus to choose a default.

Why this varying behavior from player to player, and only on various DVDs?