Isaac has essentially explained what I was getting at earlier, except much more
clearly. When I said "this allows better pipelining and backpressure down to
the network and file descriptor layer," I was essentially saying "implementing
read or write operations as cancellable and incremental does not fit well with
making them atomic operations that can fit into architecture of streams with
flow-control." And, as Isaac again eloquently pointed out, streams without flow
control are not streams at all. ("You're Missing the Point of Streams," anyone?
:P)
Another way of looking at it, is that a streaming API is itself incremental and
cancellable. It makes no sense to say that each read from or write to the
stream is *also* incremental and cancellable; why introduce another layer of
entirely-unnecessary depth before you reach the atomic level of
non-incremental, non-cancellable reads/writes? What use case does that serve?
