Parallel Dimension Model
Authors such as C.S. Lewis and Madeleine L'Engle have stated that the actual world in which the main characters live in is in no way magical. However, for some reason, certain people will be selected to be transported to another realm in which magic does exist.
What we really want to know is, how can you possibly adjust to a life absent of magic when you get back to the "real world?" It reminds us a bit of the transition certain people go through when they leave college and realize that they're not going to spend the rest of their lives partying four days a week and skipping their classes to sun on the Quad. For example, in The Lion, The Witch, and the Wardrobe, the Pevensie children grow to adult age while they're in Narnia, presumably participating in fairly adult activities, some of which they'll never again be able to do (such as throw huge banquets for their fellow Narnians, chase down deer on horses, get treated like the royals they are, and the like). They leave Narnia as adult kings and queens, and return to the world as regular British schoolchildren. If that's not a recipe for suicidal thoughts, we don't know what is.
In fiction, the only limit is the author's imagination, and so there's no reason not to combine different models to make an uber-model. For example, you could have a world where some human wizards have magical power, and there are also other non-human species that have power. Or a parallel dimension that collides with the "real world," sending emissaries of magic across the boundary.
However, what some people perceive as "creative," others often dub as "lazy." Authors like Tolkien and C.S. Lewis basically invented the fantasy genre, and spawned pretty much all that we think of as magical fantasy today. They created very specific rules and boundaries for their worlds to make them more believable. Often, modern-day authors just get sloppy. Here-a-magic, there-a-magic, everywhere-a-magic-magic!
- - Aristocratic Model: http://harrypotterwallpaper.org/wp-content/uploads/2010/05/harry-potter-wallpaper2.jpg
- - Democratic Model: http://images.amazon.com/images/P/0345345991.01.LZZZZZZZ.jpg
- - Vampire Model: http://www.thecimmerian.com/wp-content/uploads//2007/02/elves.jpg
- - Parallel Dimension Model: http://www.flickdirect.com/images/movies/lion-witch-wardrobe/lion-witch-wardrobe_1.jpg
- - Multi Model: http://farm4.static.flickr.com/3499/3460131457_96b7290ca8.jpg