Comment by watermelon0

Dumping memory state to disk (e.g. how Redis works) is another example of fork without exec.

Additionally, it can also be used in languages that don't have good support for threading (e.g. PHP) to implement parallel processing with shared memory.

However, I'd say that Redis use case is probably the only legit use case (today) of fork without execing, where benefits are huge, and there is no good replacement.