21st Century TV and Broadband in Hertfordshire

So you are sat in your living room watching Chris Froome ride a bicycle along the streets of Rio in Brazil.
Just think about that for a moment, live, high definition TV from the back of a motorcycle, on the other side of the planet.
So how come BT I can only get 2 meg broadband (narrowband as I prefer to call it) when I live 17 miles from central London?