Fandom School (5th period): Why Is My Show On Hiatus?!

I'f you've read How To Survive Hiatus and this post showcasing hiatus-induced madness (or if you're in, say, the Sherlock fandom), you know that hiatus is awful. It drives people insane, makes them lose interest in the show, and generally causes chaos. So why do it?

Here are a few reasons why producers choose to put a show on hiatus:

• Natural between-seasons break: name one show that films continuously and never takes a break. Did you come up with any? I thought not. (If you did, let me know in the comments; I'm curious.) All shows take a break in between seasons. This break can last from weeks to months- any longer than a few months, and it's a proper hiatus.
• Demand for actors/actresses: take Benedict Cumberbatch. Everyone wants him. And I'm not just talking about the Cumbercollective; he's being cast in all sorts of amazing movies and TV shows. He can't film two things at once, so he has to take a break for other things.
• Time required to write: episodes can take a long time to write, especially in the case of Sherlock. 90-minute episodes require a lot of thought, effort, and time. After all, you wouldn't want them to hurry and give you a bad product, would you?
• Time required to film: a typical episode takes longer than a week to write, so you can't air a new episode every week with no breaks. That's simple math.
• Complications: take Doctor Who for example. Every time an old Doctor leaves, a new actor has to be found to be the next Doctor. There was a break between the end of series 4 and series 5 (with a few specials, but not a regular stream of episodes), and I suspect it was because BBC was looking for someone to be the Eleventh Doctor. (I don't know if that's the reason. Does anyone know?)
• Lack of interest: if a show becomes unpopular, it may go on hiatus or even be cancelled.

That's all I got. What do you think? Did I miss anything? Justified or not, hiatus still stinks. It'll be worth the wait, though.