As a minnow of Steem I often feel like the lack of comment interaction comes from greed. People don't want to waste influence unless they think it'll make them more money or increase their following. The best way to get a good following here is to invest a good chunk of cash and using bots to comment/find/upvote/resteem (which is pretty much half the damn posts).
RE: Why aren't more authors upvoting comments on their post?