There are a benefits, but most people won't notice them without first actually using a hypermedia API.

* It's self-documenting. Client developers can find all the endpoints just by clicking around (instead of reading mountains of docs).

* Client apps don't need to keep a list of hard-coded urls for random access, removing one of the most brittle parts of client apps (they should know about rels of course, but those end up being easier to keep track of).

Once you actually use an API like this, other APIs feel like they're in the stone age and how to do things with them seems like a continual guessing game. And it's still simple as hell -- remember it's just json with links. It's not like that requires a lot of extra effort.