Some author do put effort in their fanfic like it's their precious thesis. Sometimes they think about the plot or the dialogue for a long time to make it perfect, sometimes they stay awake at night to write. Not for anyone, though, it's for themselves.

Some author make updates in 5k words, it's more than 10 pages in microsoft words. When you read it and you feel entertained, or satisfied, or happy, or glad, even when you didn't feel anything at all, it will be nice to say something, whether to say thanks for sharing the story or to point out some flaws, or simply to communicate.

I realize that I am in no place to about my story, they are not even that great, but I do feel disappointed when actually I put so much effort into my story. It's actually make me sad and discouraged.

It might happened to your favorite author too. Think about your favorite story, has one of it stopped and the author not updating anymore? Maybe they felt discouraged too, that they might feel that there are no one who actually read their story. Because what does a story mean without readers?

That is why I always make time to comment at the story I liked, not just "update soon" or "so nice" or "that's great" but one sincere comment about what i feel about the story. I think when people do this often to their favorite authors and their favorite stories, there will be less unfinished stories. Aren't you feel irritated when the story just reached its but then it stopped, and when you checked, last update was on 2011.

It might sounds demanding, but as someone who writes, I think all authors feel the same too.