I'm so upset why are they cancelling girfriends, and why are they gonna b showing the reruns on sunday night n

I had really started liking that show and gotten to know and understand all of the characters. Why does this seem to happen 2 all of the good black shows, whenever it goes off the air, it just goes off no finale or nothing friends had a big promotion for their finale and Girlfriends was just as good, on top of that it was produced & written by Kelsey Grammer (that dude fromFRASIER) I just don't get it!! It was one of the top rated shows on Monday Nights. Does anyone know why?!