Yeah, a library for a library, there's little difference, I agree; but the main point of REST is exactly the fact that the library is optional, and if necessary it can be entirely bypassed with little effort. With SOAP this is almost invariably impractical or impossible; you'll need a basic SOAP library even for sending "Hello world" back and forth. REST is more human-friendly in many ways.

Somebody could also say REST implementations usually end up passing less data around, because they usually don't require the overhead of compulsory metadata typical of SOAP standards (schemas, "envelopes" etc). This is obviously a trade-off with "exactness", but again most developers are happy to trade speed for metadata they'll rarely use (if ever). It also helps making server-side caching easier.