This is a good question. I've never been able to find the right answer.
I like to be known in my niche, it's a little rewarding to see people think of you as 'the guy who knows'.
I like getting a little side money. But I know I won't be making a living off of it.
I like getting views. It's rewarding to play with the stats and see who watches what, and why.
I like going through comments. While they're sometimes nice, it's a bit sad to see how people have lost any interest for spelling properly (with the common excuse "it's online so it doesn't matter"), and how mean they can be for no reason.