I have been guilty of that! I sometimes have not upvoted when I comment on a post with about $1 or more. I figured at that time, the post is getting some exposure and my vote could go to an insightful comment on the page or a post with less exposure.

I also will sometimes hold a vote on a post that spends as much time asking for upvotes as it does saying something worthwhile. Every post is, by default, asking for upvotes. Dedicating 25% of a post to it is kind of silly.

I occasionally won't upvote when I comment on a one line post where my comment is intended only for the author, to share with them a link to how to steemit articles or FAQ that they seem to have overlooked.

Even still, it seems like my voting power is chronically depleted because there are so many good posts and comments that I love to upvote!