The UNIX pipe has the (for many systems) undesirable negative property of losing data in the pipe when the receiving process terminates: Anything in the kernel buffer of the pipe gets lost.

Since the pipe is generally unidirectional, the sending process has no way of knowing whether the receiving process has received, or even more successfully processed, anything sent. For that, one needs to make a pipe in the opposite direction and that is not as easy anymore; it also requires building your own protocol to identify and acknowledge sent work items.