I read a lot. I do not always comment on every fic I read, although I do try to leave some kind of note on most stories, unless my opinions would simply be of no use (i.e. "wow, everyone is OOC in this fic!"). This goes double for multi-part stories, where I do not always have stuff to say for every part, so I wait until the story is done to give my feedback.
This does not make me a bad person. It makes me a human being with limited time, and same goes for everyone else like me.
I have great pity for those of you who cannot imagine writing for less comments than you expected to get. It's much more fun to work from internal motivation than for just the (elusive) fannish cookies, I think. If I set my bar at, say, 5 comments or more, half of what I write would never be posted.
p.s. flame me, and you're banned. just getting that out there.