I am under the impression that Chia NFTs enforce royalties on-chain. But I feel like no one ever talks about this. Do I understand this correctly? Is there some catch, or reason why this isn't a huge deal? How unique is this capability? Trying to understand why this isn't getting more attention...

Founder of Trick or Treat: https://trickortreat.co

Id say that not enough NFT marketplaces have gone down yet. 

And creators aren’t used to securing their royalties with NFT marketplaces.

It's correctly understood and there's no catch that i'm aware of. When you mint a NFT on Chia you simply set the royalty % and the chain will enforce it on future sales of that NFT. Quite elegant, and few in the NFT space talks about it, presumably as it's a paradigm shift rendering many current marketplaces obsolete