The most basic of everything is that REST assumes that you won't ever try to
call an operation on the resource, apart maybe from creating or destroying
it (and God forbid running an operation that is not tied to any resource at
all, or works on multiple resources at the same time). So your REST service is
basically a passive data store. Once you go outside of this realm (and more
often than not you should do so), you have remote procedures, and REST, being
a pattern instead of protocol and working on individual object, gives
you nothing useful.