The original idea behind streams is decidedly more Unix-like than the whole BSD sockets hack. Also it is only partially relevant to networking, conceptually it is generalization of the concept of line discipline, IIRC the original implementation of PTYs in SysV was layered on top of streams. Well, then there was X/Open and another standardization bodies who though that ISO OSI stack is a good thing (you have to be standards body to be capable of believing that) standardized STREAMS (note the capitalization) and build ISO OSI API in terms of that, complete with userspace layer in between that hides all the complexity in order for the thing to be actually usable.
