It was not cancelled. it still goes on at PBS Kids at 4 o'clock.
There isn't really a specific reason on why Postcards From Buster got cancelled. I think it's because of the same reason most children and regular tv programs got called.
Postcards from Buster went on hiatus in 2008, and returned in 2012 for only 3 more episodes. Probably the ratings didn’t justify to pay for any more new episodes.
Postcards from Buster - 2004 Ciao Buster Italy 3-1 was released on: USA: 7 November 2008
Postcards from Buster - 2004 Rock and Roll Boulder Colorado 1-11 was released on: USA: 8 November 2004
Postcards from Buster - 2004 Mykala Pono and Buster's Big Hawaii Show The Big Island Hawaii 2-1 was released on: USA: 27 November 2006
Postcards from Buster - 2004 Philadelphia Masala Philadelphia Pennsylvania 2-5 was released on: USA: 8 January 2007
Postcards from Buster - 2004 Best Friends Winchester Kentucky 1-17 was released on: USA: 16 November 2004
The duration of Postcards from Buster is 1800.0 seconds.
Postcards from Buster was created on 2004-10-11.
Postcards from Buster - 2004 Vamos Buster was released on: USA: 25 February 2012
Postcards from Buster - 2004 was released on: USA: 11 October 2004
Postcards from Buster - 2004 Buster in Beijing - China - 3.2 was released on: USA: 14 November 2008
Postcards from Buster - 2004 Buster in Beijing China 3-2 was released on: USA: 14 November 2008
Postcards from Buster - 2004 Ciao Buster Italy 3-1 was released on: USA: 7 November 2008
Postcards from Buster - 2004 Buster's Egyptian Adventure Egypt 3-3 was released on: USA: 21 November 2008
Postcards from Buster - 2004 Buster's Big Goal East Boston Massachusetts 1-40 was released on: USA: 1 April 2005
Postcards from Buster - 2004 Buster's Sweet Song Leiper's Fork Tennessee 1-34 was released on: USA: 3 February 2005
The family are married lesbians
Postcards from Buster - 2004 Rock and Roll Boulder Colorado 1-11 was released on: USA: 8 November 2004