The trick is that writing for Steemit is writing for Curie! One just happens to provide a nice rewards incentive for doing a great job. If you're aiming high with most of your posts, you have a better chance of attracting attention. Good content breeds good content, it's just annoying when you see people spamming memes they pulled off Facebook and self-voting their garbage into the Trending and Hot pages. :)

Good point about community engagement, too. It's why commenting is so important to begin with: not only is it a way to score some additional upvotes on top of your regular posts, but it's a way to attract new followers and grow the pool. :)