Because YOUNG PEOPLE ARE NOT WATCHING THE TELEVISION ANY MORE.
Fear not, this could be for any of the following reasons
a) There are less young people. Remember, this is why the South Will Win in the end.
b) They are downloading television directly into their branes.
c) They have all been put off by Two Pints Of Lager And A Packet of Crisps as the photo in the BBC news story suggests.