I think finales are important. They don't have to be big, planned out, endings I just like the last episode to stand out. Look at Courage the Cowardly Dog for example. The last episode gave us two GREAT episodes. The first showing us Courage's origin story. The second involing an Old Woman telling Courage he's not perfect. That episode clearly stuck out, and is a fitting way for the series to close.
Not all anime series end with grand finales, especially the cancelled ones. They however pull out last episodes that usually stick out. Just look out Big O's (let's ignore the second season for a second...) last episode. It left the series open-ended, but gives off the impression that "this is the end".