"If some people didn't self-vote they would get practically no rewards"
I agree, but I'm just curious... are rewards guaranteed on this blockchain?
I don't think they actually are. In which case, getting practically no rewards for a post or comment is perfectly normal and part of the experience here. It doesn't, in itself, justify self-upvoting.
That said, I've upvoted my own content here and there to get it above the payout cutoff, or to unhide it after someone downvoted it, and in the case of my weekly Mission: Agua-Possible post, as 100% of that goes to the project.
I think the self-upvote issue is a complicated one, and those who have power to affect change tend to be those who benefit from things staying as they are.
Also, I think if we clamp down on or reduce self-upvotes somehow, it will only encourage more inappropriate bot use, and empty sock puppet accounts, shitposts, and other chicanery.