One thing not mentioned here: discoverability.

As there are more and more APIs, more devices, and in general more complexity, computers should be talking to each other and figuring things out between themselves more. Right now almost all APIs require developers to explicitly code the interaction details. If 'RESTful' web services were actually 'RESTful' (i.e. reached level 3 on the Richardson maturity model) then we might be able to do that.

People keep saying that HATEOAS isn't ready for use yet, I'd say the only reason for that is that no one is using it. I would consider a level 3 qualifying web service to be technically far superior to the majority, and I would be more likely to use it.