A very common use case is the ability to incrementally update the value of a Task as it is being computed. Perhaps this is due to a constantly improving result (such as computing prime numbers, and each prime number computed becomes the "value" until the next prime is computed). More often this is because the code is fetching many records and populating an ObservableList with results. The Task however doesn't allow for this. Although the developer can add their own support, it violates encapsulation (requires them to have their GUI code reference their specific Task instead of the generic Task) and is actually hard to do without flooding the event queue.