Voting just for promotion rewards is definitely a trend. I remember feeling pressure to try to get curation rewards when I first started because I wanted to increase my Steem Power. Speaking for myself, though, I don't always comment for time reasons. Sometimes I scan content and vote on a bathroom break or between classes, other times I start to comment and get interrupted, time just doesn't always allow for us to engage in the comments. They are the most rewarding part of this platform, though. I love having a post with lots of interaction on it. It's great!