If hours of progress vanish when the game ends, nobody plays a second time. For a map like that, saving is not a feature - it is the condition the map exists under.
It is also hard to add later, because what you save shapes how your counters are designed. Bolting it on at the end usually means rebuilding the counter layout first.
That is why this module sits here rather than next to publishing. From the moment you lay out your triggers, ask of each value whether it is one that has to survive.