1. Fiction is fictional. This means now matter how realistic it's supposed to be, it's only vaguely based on reality.
2. In fiction, people have to talk which makes it not so easy to portray introverted characters.
3. Many pieces of media are written by several authors and everyone will interprete the given characters differently.
4. Authors are just people too. There is no one to stop them in case they create obviously contradictory characters. Which means also that they have to act extreme because otherwise they wouldn't be interesting enough. Let's face it, if one would meet someone who acts like a character from fiction people would say He sure has issues!
This pretty much sums up what I think. Most television show writers aren't making a character based on an MBTI type, and the character has to fit the template of a television show, ie
stuff has to be happening constantly. To say that a television character isn't realistic is like saying the events and situations of a television show are not realistic; people aren't watching for the realism. You'll be hard pressed to find people that will run into a burning building to save someone, but on TV
everyone will, because it's more exciting.
I've always found it funny when people try to type the characters on Family Guy because all of them do so many things that are rather "out of character", but in my opinion this is probably more accurate (although not to the same extreme). Television characters are often almost too static in how they act, where people in real life will be more "out of character" - we all act differently depending on who we are around, where TV characters are usually themselves around everybody.
But, on a side note, I'd say House is probably one of the easiest characters to type, and I'd say he's INTJ. He
is introverted (keeps his problems to himself, hates talking to patients, never gives speeches/lectures). Ni because of his convergent way of thinking, generally ending in some sort of epiphany. TJ because he has a tendency to change or manipulate reality to fit his internal logic (rather then the Ti way of creating logical internal models of reality)
