Even curation isn't guaranteed as we've seen with certain accounts autodownoting certain other accounts. Just cause you have delegated HP doesn't change the fact that if you curate garbage content someone may go and downvote everything you've voted on.
I didn't need to mention that curation rewards aren't guaranteed with delegated stake since it's the same as curating with your own stake.
as for leofinance, not sure what they do with the HP they earn or how come their returns are higher by selling earned leo back to hive but there too if they curate garbage it's going to affect their apr eventually too not to mention the authors.