Because Every series has to end eventually that's just like you saying why did they end Star Trek Voyager, Star Trek Deep Space Nine, Star Trek The Next Generation, Star Trek the Origianl Series.
Did you ever think of that
A series finale is the last or final episode of a television program.
The series finale called "Graduation" aired in the US on the 6th of May, 2011
Yes they do!!! They get together in the series 3 finale titled "Finale".
1983
Friends
The fourth book in the Hush Hush series is called "Finale."
november 2012
X-Play - 2003 Series Finale was released on: USA: 23 January 2013
Attack of the Show - 2005 Series Finale was released on: USA: 23 January 2013
It is the season finale episode of season 2 entitled "into the woods"
The End of the Rainbow
The final two episodes had an audience of 76 million people. It was the third highest series finale in the US.