You're exactly right!
Where I go to look and see if the commenter has replied AND upvoted, I noticed something...
michelle.gent curation reward: 0.025 SP for @sequeira/re-michellegent
I got a reward for upvoting your comment. It was a small reward, but a reward, nonetheless.
This is what people don't seem to realise.
You give and you receive.
It really is that simple.