Part of the charm and appeal of fairy tales is the magic, the fantasy, the whimsy, etc. Trying to make these characters too "logical" and literal takes all of those qualities away. As in any good story, we should be able to see ourselves (and familiar human behaviors) in these characters without having to have it all explained to us. I think it's much more effective to wonder for ourselves about the characters' backstories, etc.
Even a show like Into The Woods, which lets us explore the inner thoughts and motivations of the characters more than we normally might, doesn't work so hard to make them "relevant" - that relevance can be felt and imagined as I said above, but it's not spelled out so literally. And when the story starts getting a little "analytical" ("I was only trying to be a good mother" comes to mind) it's usually done with humor instead of over-earnestness.