Themes ain't wot they used to be

Theme parks have to have theme's, right? They have seperate areas of the park dedicated to specific subjects. Sort of. Hopefully, themes and characters that punters can identify with.

So why are they always so out of date? A Harry Potter theme park opens when the Harry Potter craze is at an end. Alton Towers and Thorpe park open new horror film related rides when teenage girls are obsessed with vampires. I'm sure you can think of more examples. Christ...why isn't there a Doctor Who theme park or area in England? Where are the Twilight or Trueblood themed rides? Maybe even a Facebook ride where you can update your status as you ride?