I have read so many books with characters who just disappear and you never know what happened to them. I want to know what happens to all the characters created. In my mind if they were created they have a purpose for being in the story so they deserve for their stories to be told as well.
The creation of a character takes time and thought, so why would you create one and leave your readers hanging wondering what happened to them. When I read I notice when a character is just left off with no ending and it drives me nuts.
It is one thing to have cliff hangers, however, those cliff hangers shouldn't be what happened to a character if there isn't going to be another book or addition to the story. All characters have a beginning, they should have an end as well.