It's useful still! If you have an application that talks to another application on the other side of the world, you get to control how fast it sends you stuff w

It's useful still! If you have an application that talks to another application on the other side of the world, you get to control how fast it sends you stuff with your reading speed. If you stop reading from the socket, the sending application will stop sending before long. It seems like spooky action at a distance but it's just backpressure propagating through many layers.