In programming usually a (non-crypto-safe) RNG returns the same sequence everytime it is started with the same seed. Therefore, you often seed with the current time if you do not want to have reproducable sequences and use a specific seed when you want reproducable results across certain runs.
There are meany causes to want to have this deterministic “randomnes”:
* As mentioned in this thread: reproducable results across different systems, OSs and architectures
* Certain kinds of games do transfer/save a base seed instead of the randomly generated level to save bandwith/diskspace
There are more examples, but in the end, they all rely on reproducing the sequence over multiple architectures to recreate something exactly the same way it was before.